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What is PHP?
PHP (recursive acronym for "PHP: Hypertext Preprocessor") is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.
How PHP came into being
PHP started as a quick Perl hack written by Rasmus Lerdorf in late 1994. Over the next two to three years, it evolved into what we today know as PHP/FI 2.0. PHP/FI started to get a lot of users, but things didn't start flying until Zeev Suraski and Andi Gutmans suddenly came along with a new parser in the summer of 1997, leading to PHP 3.0. PHP 3.0 defined the syntax and semantics used in both versions 3 and 4.
Why yet another language?
People often ask "why invent yet another language; don't we have enough of them out there"? It is simply a matter of "the right tool for the right job". Many Web developers found that existing tools and languages were not ideal for the specific task of embedding code in markup. Those developers collaborated to develop a server-side scripting language which they felt would be ideal for developing dynamic Web-based sites and applications.
PHP was created with these particular needs in mind. Moreover, PHP code was developed for embedment within HTML. In doing so, it was hoped that benefits such as quicker response time, improved security, and transparency to the end user would be achieved. PHP has evolved into a language, or maybe even an
environment, that has a very specific range of tasks in mind. For this, PHP is, in Stig's humble opinion, pretty close to the ideal tool.
For More Information
The following resources will further your knowledge of PHP:
The PHP Manual: http://www.php.net/manual/en/
The PHP FAQ: http://tr2.php.net/faq
PHP Notes 1 Lakshman Gupta 8:57 AM 10/8/2019
PHP Tutorial
Language Syntax
Most of PHP's syntax is borrowed from C, although there are elements borrowed from Perl, C++ and Java as
well. This article assumes that you are familiar with C's syntax. However, don't panic if you're not.
Embedding PHP Code
To give you an idea of what embedding PHP would entail, consider the following three "hello world" examples,
all of which will give the exact same output:
Example 1: HTML alone
Hello, World!
Example 2: PHP code alone
<?php print "Hello, World!"; ?>
Example 3: PHP embedded within HTML
<?php print "Hello,"; ?> World!
Web servers supporting PHP will, by default, scan a file in HTML mode. HTML code will be passed over to the
browser as usual, up until the server happens upon a PHP line of code. In examples 2 and 3 above, the "<?php" tag informs the server that PHP code is to follow. The server then switches over to PHP mode in
anticipation of a PHP command. The "?>" tag closes out the PHP mode with the server resuming its scanning in HTML mode once more.
Embedding code in this manner is, conceptually, a more fluid approach to designing a Web page because you are working within the output setting, namely an HTML page. Traditionally, you had to fragment the output (i.e. the header, body, footer etc..) and then put it into the code. Now we are inserting the code directly into the output.
"So, what's the difference?" or "Why add extra code when HTML alone would do the trick?".
Dynamic vs. Static Web pages
The "Hello, World" example we chose would certainly not require you to use PHP. That's because it is static, meaning its display will always remain the same. But what if you wanted to greet the world in any number of
ways? Say, for example, "Bonjour, World!", or "Yo, World!" and so on.
Since HTML tags are purely descriptive they cannot function as a variable. Nor can they convey even the simplest of uncertainty such as a "Bonjour" or a "Yo". You need a command language to handle variability in a
Web page. Based on either a conditional statement or direct user input, a command language can generate the
"static" HTML necessary to correctly display a Web page's content.
Let us reconsider example #3. This time we want to let the user decide how to greet the world:
Example 4: PHP embedded within HTML revisited!
<?php print $greeting, ", "; ?> World!
From the above example, $greeting is assigned a value, and together with the comma and the word "World!",
this value is sent to the browser.
Dynamic Web page design, however, is more than just about inserting variables. What if you wanted not only to
greet the world in French, but also to present the page using the colors of the French flag?
Both a Web page's structure as well as its content can be customized. This means dynamic Web page
programming can also entail on-demand Web page building. No static, here!
Variables In PHP, a variable does not require formal declaration. It will automatically be declared when a value is assigned to it. Variables are prefixed by a dollar sign: ($VariableName).
Variables do not have declared types. A variable's type does not have to be fixed, meaning it can be changed over the variable's lifetime. The table below list's PHP's variable types:
Type Description
Integer integer number
Double floating point number
bool1 Boolean (true or false), available from PHP 4.0
Array hybrid of ordered array and associative array
object2 an object with properties and methods (not discussed in this article)
PHP Tutorial
In the following example, four variables are automatically declared by assigning a value to them:
<?php
$number = 5;
$string1 = "this is a string\n";
$string2 = 'this is another "string"';
$real = 37.2;
?>
Strings
The string constants may be enclosed between double-quotes ( " ) or single-quotes ( ' ).
In a double-quote enclosed string, the variable conversion is done automatically.
$city = "Ankara";
print "I live in $city.";
$height = 182;
print "I am $height cm tall.";
String operators: Concatenation: . Concatenation to the end: .=
$str1 = $lastname . ", " . $firstname;
$str2 .= $str3;
Arrays
PHP supports two type of arrays:
· Numerically indexed arrays
· Associative arrays.
Numerically indexed arrays:
The indices in numerically indexed arrays starts from 0 by default, although this can be altered.
The elements of an array can be of various data types. Integers, doubles and strings can be used in the
same array.
There is no declaration of size. All arrays are dynamic in PHP.
Creation of arrays:
$ar1 = array (); // here an empty array is created.
$ar2 = array (7, 12, 20, 32); // an array with indices 0 to 3
$ar3 = array (12, "January", 2008, 16.40); // array with various data types
$ar4 = array(5 => "five", "six", "seven"); // an array with indices 5 to 7
Accessing array contents:
print $ar2[2]; // 20 is output
$ar3[2] = 2009; // value of the element with index 2 is changed
$ar1[0] = "Adana"; // an element is added to $ar1
$ar3[4] = "East"; // an element is added to $ar3
printf("7: %d, 1: %d, 'six': %s\n", $array1[3], $array2["one"], $array3[6]);
foreach ($ar3 as $v)
{ print "$v<br />"; } // all values of the array are output
Associative Arrays
Associative arrays has two part: keys and values. The keys are indices of the array.
Both the keys and values can be of any data type in the same array.
=> operator is used to combine the key and the value of an element of an associative array.
Creation of associative arrays:
$as1 = array(24 => "Ram", "Lakshman" => 844, "Pi" => 3.14159);
$as2 = array(20458444 => "Ali Ak", 20487542 => "Ayse Bal");
Accessing array contents:
print $as1["Lakshman"]; // outputs: 844
$as1[24] = "Ram"; // value of element with key=24 is changed.
$as2[20608888] = "Fatmai"; // a new element is added to array.
foreach ($as2 as $id => $name)
{ print "<b>$id</b>: $name<br />"; } // all keys and values are used
foreach ($as4 as $k => $v)
{ $as4[$k] = $v + 7; } // all values of array $as4 are increased by 7
keys values
24 "Ram"
"Lakshman"
"Pi" 3.14159
PHP Tutorial
Conditionals and Looping Constructs
PHP includes if and elseif conditionals, as well as while and for loops, all with syntax similar to C. The example
below introduces these four constructs:
// Conditionals
if ($a)
{
print "a is true<br/>\n";
}
else if ($b)
{
print "b is true<br/>\n";
}
else
{
print "neither a or b is true<br/>\n";
}
// Loops
for ($j = 0; $j < 10; $j++)
{
print "j = $j<br />\n";
}
while ($d)
{
print "ok<br />\n";
$d = test_something();
}
do
{
$c = test_something();
} while ($c);
Array Traverse Constructs:
foreach ($array as $value) {...} // To traverse elements (values) in an array.
{ .... }
foreach ($array as $key => $value) {...} // To traverse elements (key + value) in an associative array.
{ .... }
Operators
Assignment operators: = += -= *= /= .= (string concatenation)
Arithmetic Operators
Example Name Result
$a + $b Addition Sum of $a and $b.
$a - $b Subtraction Difference of $a and $b.
$a * $b Multiplication Product of $a and $b.
$a / $b Division Quotient of $a and $b.
$a % $b Modulus Remainder of $a divided by $b.
Incrementing/Decrementing Operators
Example Name Effect
++$a Pre-increment Increments $a by one, then returns $a.
$a++ Post-increment Returns $a, then increments $a by one.
--$a Pre-decrement Decrements $a by one, then returns $a.
$a-- Post-decrement Returns $a, then decrements $a by one.
PHP Tutorial
Comparison Operators
Example Name Result
$a == $b Equal TRUE if $a is equal to $b.
$a != $b Not equal TRUE if $a is not equal to $b.
$a <> $b Not equal TRUE if $a is not equal to $b.
$a < $b Less than TRUE if $a is strictly less than $b.
$a <= $b Less than or equal to TRUE if $a is less than or equal to $b.
$a > $b Greater than TRUE if $a is strictly greater than $b.
$a >= $b Greater than or equal to TRUE if $a is greater than or equal to $b.
$a === $b Identical TRUE if $a is equal to $b, and they are of the same type. (PHP 4 only)
$a !== $b Not identical TRUE if $a is not equal to $b, or they are not of the same type. (PHP 4 only)
Logical Operators
Example Name Result
$a && $b And TRUE if both $a and $b are TRUE.
$a and $b And TRUE if both $a and $b are TRUE.
$a || $b Or TRUE if either $a or $b is TRUE.
$a or $b Or TRUE if either $a or $b is TRUE.
! $a Not TRUE if $a is not TRUE.
$a xor $b Xor TRUE if either $a or $b is TRUE, but not both.
String operators: Concatenation: . Concatenation to the end: .=
$str1 = $lastname . ", " . $firstname;
$str2 .= $str3;
Functions
Function declaration:
function my_func ()
{
print "Hello Lakshman!";
} // end function my_func
Function parameters and returning values:
function count_a ($str)
{
$n = substr_count($str, "a");;
return ($n);
} // end function count_a
Function parameters - passing parameters by reference and by value:
function salary_increase (&$value, $inc_rate)
{
$value *= (1 + $inc_rate);
} // end function salary_increase
Returning arrays:
function get_values ($a, $b)
{
$vals = array();
// ...
// statements to put values into the array $vals
// ...
return ($vals);
} // end function get_values
Calling the function:
my_func();
Calling the function:
$x = count_a ($name);
Calling the function:
salary_increase ($salary, 0.1);
Calling the function:
$xarr = get_values ($k, $m); // Here, $xarr becomes an array
PHP Tutorial
File System Functions:
Open File $fp = fopen(“filename”, “mode”); Open a file, where mode is either “r”,
“w” or “a”
Close File fclose ($fp);
Read a line from file $line = fgets($fp, 4096);
Write a string to a file fwrite ($fp, $string);
Read all the lines of a
file
$line = fgets($fp, 4096);
while(!feof($fp))
{ print "$line<br />\n";
$line = fgets($fp, 4096);
}
Reads line by line while NOT end-offile.
Read all the lines of a
file
$lines = file ('filename');
foreach ($lines as $line) { print $line; }
Reads all the lines of the file in an
array; then print the lines.
Delete a file unlink ('filename');
See http://www.php.net/manual/en/ref.filesystem.php for more information.
Web Application Features
One of PHP's oldest features is the ability to make HTML form and cookie data available directly to the
programmer. By default, any form entry creates a global PHP variable of the same name.
In the following example, a user name is retrieved and assigned to a variable. The name is then printed by the
sub-routine "submit.php":
<FORM ACTION="submit.php" METHOD="post">
What's your name? <INPUT NAME="myname" SIZE=3>
<br /> <input type="submit" value=" SUBMIT " name="btn_submit">
</FORM>
submit.php
<?php
print "Hello, $myname!";
?>
Working With Cookies
HTTP cookies (or just cookies) are parcels of text sent by a server to a Web client (usually a browser) and then
sent back unchanged by the client each time it accesses that server.
Each cookie has a name and value. It may also have an expiration time.
Cookies are sent by web server inside the HTTP response before any html content.
Cookies are stored in the client computer.
In PHP, to create cookie, the function setcookie is used. Example:
setcookie ("ck_cnt", $count, time()+3600*24*365); // expires in a year
In PHP, the cookies can be accessed using the super global variable $_COOKIE.
The PHP statement: extract ($_COOKIE);
creates variables with the names of cookies containing their respective values.
HTTP cookies are used for authenticating, session tracking (state maintenance), and maintaining Specific
information about users, such as site preferences or the contents of their electronic shopping carts.
The PHP function setcookie() adds headers to the HTTP response. Since headers must be inserted before the
body, all setcookie() calls must be performed before any body output (usually HTML) is printed.
The following example uses a cookie to store a form value until your browser is terminated.
<?php
if (isset($myname))
{
setcookie("myname", $myname);
}
print <<<_A_
PHP Tutorial
<html>
....
_A_;
....
?>
The following example displays all the cookies releated with the visited site:
<?php
if (!$_COOKIE) { $_COOKIE = $HTTP_COOKIE_VARS; }
foreach ($_COOKIE as $ck => $val)
{ print "<dd>Cookie name: $ck; value: $val<br />\n"; }
?>
Examples:
· Webmail: store and use username.
· Weather Site: store the selected city in a cookie, and next time the site is visited, the weather of the
stored city is automatically displayed.
Built-in Variables
PHP has a number of built-in variables that give you access to your Web server's CGI environment,
form/cookie data and PHP internals. Here are some of the most useful variables:
PHP internal variables
The $GLOBALS and $PHP_SELF variables shown in the table below are specific to PHP:
Variable
Name
Description
$GLOBALS An associative array of all global variables. This is the only variable in PHP that is available
regardless of scope. You can access it anywhere without declaring it as a global first.
$PHP_SELF This is the current script, for example /~ssb/phpinfo.php3.
$_POST An associative array of POST variables.
$_GET An associative array of GET variables.
$_COOKIE An associative array of COOKIE variables.
$_SERVER An associative array of SERVER variables.
CGI / Web server provided variables
The variables listed below are derived from CGI protocols.
Variable Name Description
$DOCUMENT_ROOT Your Web server's base directory with user-visible files.
$REQUEST_METHOD The HTTP method used to access this page, for example GET or POST.
$REQUEST_URI Full local part of the request URL, including parameters.
$SCRIPT_FILENAME File name of the top-level page being executed.
$SCRIPT_NAME Local URI part of the page being executed.
$SERVER_NAME Domain name for the server.
$SERVER_PORT TCP port number the server runs on.
HTTP Request Variables
HTTP Request Variables are derived from their corresponding HTTP headers.
$REMOTE_ADDR IP address of the client (browser) machine
$HTTP_HOST Host name in the browser's "location" field.
$HTTP_USER_AGENT User agent (browser) being used.
$HTTP_REFERER URL of the referring page.
PHP Tutorial
Regular Expressions
Regular expressions, a powerful tool for manipulating text and data, are found in scripting languages, editors,
programming environments, and specialized tools.
Special characters: "/" "-" "^" "." "\" "^" "$" "*" "+" "(" ")"
Equivalent Description or Meaning Examples
/abc/ search for substring "abc"
/[akt]/ search for one of "a", "k" or "t".
/[^akt]/ true if string do not have any one of "a", "k" or "t".
/[0-4]/ /[01234]/ search for one of "0", "1", "2", "3" or "4"
/.../i Case insensitive
* Zero or more /abck*pqr/
+ One or more /abck+pqr/
\d [0-9] Any decimal digit [0123456789]
\D Any character that is not a decimal digit
\w [0-9A-Za-z_] Alphanumerics and underscore
\W Any "non-word" character
\s [ \r\t\n\f] Any Whitespace character
\S Any character that is not a whitespace character
\b At word boundary (at the beginning or end) /\babc/ or /abc\b/ or /\babc\b/
\r Return (CR)
\f Linefeed (LF)
\n New line (CRLF)
\t Tab
/^.../ Starts with /^klm/
/...$/ Ends with /ali$/ /^good$/i
/\d{4}/ 4 digits /\d\d\d\d/ /[A-Z]{3}\d{3}/
/\d{2,4}/ 2 to 4 digits /\d{2} [A-Z]{1,3} \d{2,4}/
(...) Grouping
Regular Expression Functions in PHP
preg_match: Perform a regular expression match
Examples:
// The "i" after the pattern delimiter indicates a case-insensitive search
if (preg_match ("/php/i", "PHP is the web scripting language of choice."))
{
print "A match was found.";
}
else
{
print "A match was not found.";
}
// The \b in the pattern indicates a word boundary, so only the distinct
// word "web" is matched, and not a word partial like "webbing" or "cobweb"
if (preg_match ("/\bweb\b/i", "PHP is the web scripting language of choice."))
{
print "A match was found.";
}
else
{
print "A match was not found.";
}
if (preg_match ("/\bweb\b/i", "PHP is the website scripting language of choice."))
{
print "A match was found.";
}
else
{
print "A match was not found.";
}
preg_replace: Perform a regular expression search and replace
Examples:
$string = 'April 15, 2003';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '${1}1,$3';
print preg_replace($pattern, $replacement, $string); // PHP Notes PHP Tutorial
Database Handling
Communication with MySQL
PHP and MySQL are often referred to as the "dynamic duo" of dynamic Web scripting. PHP and MySQL work
very well together, in addition to the speed and features of each individual tool.
The steps in using MySQL databases in PHP are as follows:
1. Connect to MySQL Server and select database (usually placed in main of the PHP scripts):
$dblink = mysql_connect("localhost", "db_user", "my_password") or die("Could not connect");
mysql_select_db("my_db") or die("Can not select database");
2. Prepare and submit a query:
$query = "select * from person where p_city = '$city'
order by p_lname";
$qno = mysql_query($query) or die("Query error: <b>$query</b><hr />" . mysql_error());
3. Get number of records selected / affected:
$n = mysql_num_rows ($qno); // Get number of records affected.
4. Fetch data from database server:
while ($record = mysql_fetch_assoc($qno))
{
extract($record); // Create variables by table column names
........ // Use these created variables
}
5. Free the query resources:
mysql_free_result ($qno); // Free query result set.
6. Close connection to database server:
mysql_close($dblink); // Close connection.
MySQL Example
The following is a simple example of how to dump the contents of a MySQL table using PHP. The example assumes you have a MySQL user called "db_user" who can connect with password "my_password" from localhost. In the example below, PHP implements the following procedure:
<?php
// Connect and select database:
$dblink = mysql_connect("localhost", "db_user", "my_password")
or die("Could not connect");
mysql_select_db("my_db") or die("Can not select database");
// Perform SQL query:
$query = "select * from user";
$qno = mysql_query($query)
or die("Query failed: $query<hr />" . mysql_error();
$n = mysql_num_rows ($qno); // Get number of records selected/affected.
// Output results in HTML:
print "<table border='1'>\n";
while ($user = mysql_fetch_assoc($qno)) // While a record is retrieved...
{
// Print column headings if first row
if (!$header_printed)
{
print "\t<tr>\n";
$fields = array_keys ($user);PHPNotes 8 Lakshman Gupta 9:48 AM 10/8/2019
reset($user); // Rewind for the next foreach
foreach ($fields as $field)
{
print " <th>$field</th>\n"; }
print " </tr>\n";
$header_printed = true;
} // end of print header.
// Output data in the record retrieved.
print "\t<tr>\n";
foreach ($user as $col_value)
{
print "\t\t<td>$col_value</td>\n"
}
print "\t</tr>\n";
}
print "</table>\n";
mysql_free_result($qno); // Free resultset.
mysql_close($dblink); // Close connection.
?>
Communication with Other Databases
Unlike other scripting languages for Web page development, PHP is open-source, cross-platform, and offers excellent connectivity to most of today's common databases including Oracle, Sybase, MySQL, ODBC (and others). PHP also offers integration with various external libraries which enable the developer to do anything from generating PDF documents to parsing XML.
PHP Notes
PHP Notes 1 Lakshman Gupta 9:16 AM 10/8/2019
What is PHP?
PHP (recursive acronym for "PHP: Hypertext Preprocessor") is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.
How PHP came into being
PHP started as a quick Perl hack written by Rasmus Lerdorf in late 1994. Over the next two to three years, it evolved into what we today know as PHP/FI 2.0. PHP/FI started to get a lot of users, but things didn't start flying until Zeev Suraski and Andi Gutmans suddenly came along with a new parser in the summer of 1997, leading to PHP 3.0. PHP 3.0 defined the syntax and semantics used in both versions 3 and 4.
Why yet another language?
People often ask "why invent yet another language; don't we have enough of them out there"? It is simply a matter of "the right tool for the right job". Many Web developers found that existing tools and languages were not ideal for the specific task of embedding code in markup. Those developers collaborated to develop a server-side scripting language which they felt would be ideal for developing dynamic Web-based sites and applications.
PHP was created with these particular needs in mind. Moreover, PHP code was developed for embedment within HTML. In doing so, it was hoped that benefits such as quicker response time, improved security, and transparency to the end user would be achieved. PHP has evolved into a language, or maybe even an
environment, that has a very specific range of tasks in mind. For this, PHP is, in Stig's humble opinion, pretty close to the ideal tool.
For More Information
The following resources will further your knowledge of PHP:
The PHP Manual: http://www.php.net/manual/en/
The PHP FAQ: http://tr2.php.net/faq
PHP Notes 1 Lakshman Gupta 8:57 AM 10/8/2019
PHP Tutorial
Language Syntax
Most of PHP's syntax is borrowed from C, although there are elements borrowed from Perl, C++ and Java as
well. This article assumes that you are familiar with C's syntax. However, don't panic if you're not.
Embedding PHP Code
To give you an idea of what embedding PHP would entail, consider the following three "hello world" examples,
all of which will give the exact same output:
Example 1: HTML alone
Hello, World!
Example 2: PHP code alone
<?php print "Hello, World!"; ?>
Example 3: PHP embedded within HTML
<?php print "Hello,"; ?> World!
Web servers supporting PHP will, by default, scan a file in HTML mode. HTML code will be passed over to the
browser as usual, up until the server happens upon a PHP line of code. In examples 2 and 3 above, the "<?php" tag informs the server that PHP code is to follow. The server then switches over to PHP mode in
anticipation of a PHP command. The "?>" tag closes out the PHP mode with the server resuming its scanning in HTML mode once more.
Embedding code in this manner is, conceptually, a more fluid approach to designing a Web page because you are working within the output setting, namely an HTML page. Traditionally, you had to fragment the output (i.e. the header, body, footer etc..) and then put it into the code. Now we are inserting the code directly into the output.
"So, what's the difference?" or "Why add extra code when HTML alone would do the trick?".
Dynamic vs. Static Web pages
The "Hello, World" example we chose would certainly not require you to use PHP. That's because it is static, meaning its display will always remain the same. But what if you wanted to greet the world in any number of
ways? Say, for example, "Bonjour, World!", or "Yo, World!" and so on.
Since HTML tags are purely descriptive they cannot function as a variable. Nor can they convey even the simplest of uncertainty such as a "Bonjour" or a "Yo". You need a command language to handle variability in a
Web page. Based on either a conditional statement or direct user input, a command language can generate the
"static" HTML necessary to correctly display a Web page's content.
Let us reconsider example #3. This time we want to let the user decide how to greet the world:
Example 4: PHP embedded within HTML revisited!
<?php print $greeting, ", "; ?> World!
From the above example, $greeting is assigned a value, and together with the comma and the word "World!",
this value is sent to the browser.
Dynamic Web page design, however, is more than just about inserting variables. What if you wanted not only to
greet the world in French, but also to present the page using the colors of the French flag?
Both a Web page's structure as well as its content can be customized. This means dynamic Web page
programming can also entail on-demand Web page building. No static, here!
Variables In PHP, a variable does not require formal declaration. It will automatically be declared when a value is assigned to it. Variables are prefixed by a dollar sign: ($VariableName).
Variables do not have declared types. A variable's type does not have to be fixed, meaning it can be changed over the variable's lifetime. The table below list's PHP's variable types:
Type Description
Integer integer number
Double floating point number
bool1 Boolean (true or false), available from PHP 4.0
Array hybrid of ordered array and associative array
object2 an object with properties and methods (not discussed in this article)
PHP Notes 2 Lakshman Gupta 8:59 AM 10/8/2019
PHP Tutorial
In the following example, four variables are automatically declared by assigning a value to them:
<?php
$number = 5;
$string1 = "this is a string\n";
$string2 = 'this is another "string"';
$real = 37.2;
?>
Strings
The string constants may be enclosed between double-quotes ( " ) or single-quotes ( ' ).
In a double-quote enclosed string, the variable conversion is done automatically.
$city = "Ankara";
print "I live in $city.";
$height = 182;
print "I am $height cm tall.";
String operators: Concatenation: . Concatenation to the end: .=
$str1 = $lastname . ", " . $firstname;
$str2 .= $str3;
Arrays
PHP supports two type of arrays:
· Numerically indexed arrays
· Associative arrays.
Numerically indexed arrays:
The indices in numerically indexed arrays starts from 0 by default, although this can be altered.
The elements of an array can be of various data types. Integers, doubles and strings can be used in the
same array.
There is no declaration of size. All arrays are dynamic in PHP.
Creation of arrays:
$ar1 = array (); // here an empty array is created.
$ar2 = array (7, 12, 20, 32); // an array with indices 0 to 3
$ar3 = array (12, "January", 2008, 16.40); // array with various data types
$ar4 = array(5 => "five", "six", "seven"); // an array with indices 5 to 7
Accessing array contents:
print $ar2[2]; // 20 is output
$ar3[2] = 2009; // value of the element with index 2 is changed
$ar1[0] = "Adana"; // an element is added to $ar1
$ar3[4] = "East"; // an element is added to $ar3
printf("7: %d, 1: %d, 'six': %s\n", $array1[3], $array2["one"], $array3[6]);
foreach ($ar3 as $v)
{ print "$v<br />"; } // all values of the array are output
Associative Arrays
Associative arrays has two part: keys and values. The keys are indices of the array.
Both the keys and values can be of any data type in the same array.
=> operator is used to combine the key and the value of an element of an associative array.
Creation of associative arrays:
$as1 = array(24 => "Ram", "Lakshman" => 844, "Pi" => 3.14159);
$as2 = array(20458444 => "Ali Ak", 20487542 => "Ayse Bal");
Accessing array contents:
print $as1["Lakshman"]; // outputs: 844
$as1[24] = "Ram"; // value of element with key=24 is changed.
$as2[20608888] = "Fatmai"; // a new element is added to array.
foreach ($as2 as $id => $name)
{ print "<b>$id</b>: $name<br />"; } // all keys and values are used
foreach ($as4 as $k => $v)
{ $as4[$k] = $v + 7; } // all values of array $as4 are increased by 7
PHP Notes 3 Lakshman Gupta 9:16 AM 10/8/2019
keys values
24 "Ram"
"Lakshman"
"Pi" 3.14159
PHP Tutorial
Conditionals and Looping Constructs
PHP includes if and elseif conditionals, as well as while and for loops, all with syntax similar to C. The example
below introduces these four constructs:
// Conditionals
if ($a)
{
print "a is true<br/>\n";
}
else if ($b)
{
print "b is true<br/>\n";
}
else
{
print "neither a or b is true<br/>\n";
}
// Loops
for ($j = 0; $j < 10; $j++)
{
print "j = $j<br />\n";
}
while ($d)
{
print "ok<br />\n";
$d = test_something();
}
do
{
$c = test_something();
} while ($c);
Array Traverse Constructs:
foreach ($array as $value) {...} // To traverse elements (values) in an array.
{ .... }
foreach ($array as $key => $value) {...} // To traverse elements (key + value) in an associative array.
{ .... }
Operators
Assignment operators: = += -= *= /= .= (string concatenation)
Arithmetic Operators
Example Name Result
$a + $b Addition Sum of $a and $b.
$a - $b Subtraction Difference of $a and $b.
$a * $b Multiplication Product of $a and $b.
$a / $b Division Quotient of $a and $b.
$a % $b Modulus Remainder of $a divided by $b.
Incrementing/Decrementing Operators
Example Name Effect
++$a Pre-increment Increments $a by one, then returns $a.
$a++ Post-increment Returns $a, then increments $a by one.
--$a Pre-decrement Decrements $a by one, then returns $a.
$a-- Post-decrement Returns $a, then decrements $a by one.
PHP Notes 4 Lakshman Gupta - 08/10/2009
PHP Tutorial
Comparison Operators
Example Name Result
$a == $b Equal TRUE if $a is equal to $b.
$a != $b Not equal TRUE if $a is not equal to $b.
$a <> $b Not equal TRUE if $a is not equal to $b.
$a < $b Less than TRUE if $a is strictly less than $b.
$a <= $b Less than or equal to TRUE if $a is less than or equal to $b.
$a > $b Greater than TRUE if $a is strictly greater than $b.
$a >= $b Greater than or equal to TRUE if $a is greater than or equal to $b.
$a === $b Identical TRUE if $a is equal to $b, and they are of the same type. (PHP 4 only)
$a !== $b Not identical TRUE if $a is not equal to $b, or they are not of the same type. (PHP 4 only)
Logical Operators
Example Name Result
$a && $b And TRUE if both $a and $b are TRUE.
$a and $b And TRUE if both $a and $b are TRUE.
$a || $b Or TRUE if either $a or $b is TRUE.
$a or $b Or TRUE if either $a or $b is TRUE.
! $a Not TRUE if $a is not TRUE.
$a xor $b Xor TRUE if either $a or $b is TRUE, but not both.
String operators: Concatenation: . Concatenation to the end: .=
$str1 = $lastname . ", " . $firstname;
$str2 .= $str3;
Functions
Function declaration:
function my_func ()
{
print "Hello Lakshman!";
} // end function my_func
Function parameters and returning values:
function count_a ($str)
{
$n = substr_count($str, "a");;
return ($n);
} // end function count_a
Function parameters - passing parameters by reference and by value:
function salary_increase (&$value, $inc_rate)
{
$value *= (1 + $inc_rate);
} // end function salary_increase
Returning arrays:
function get_values ($a, $b)
{
$vals = array();
// ...
// statements to put values into the array $vals
// ...
return ($vals);
} // end function get_values
PHP Notes 5 Lakshman Gupta 9:24 AM 10/8/2019
Calling the function:
my_func();
Calling the function:
$x = count_a ($name);
Calling the function:
salary_increase ($salary, 0.1);
Calling the function:
$xarr = get_values ($k, $m); // Here, $xarr becomes an array
PHP Tutorial
File System Functions:
Open File $fp = fopen(“filename”, “mode”); Open a file, where mode is either “r”,
“w” or “a”
Close File fclose ($fp);
Read a line from file $line = fgets($fp, 4096);
Write a string to a file fwrite ($fp, $string);
Read all the lines of a
file
$line = fgets($fp, 4096);
while(!feof($fp))
{ print "$line<br />\n";
$line = fgets($fp, 4096);
}
Reads line by line while NOT end-offile.
Read all the lines of a
file
$lines = file ('filename');
foreach ($lines as $line) { print $line; }
Reads all the lines of the file in an
array; then print the lines.
Delete a file unlink ('filename');
See http://www.php.net/manual/en/ref.filesystem.php for more information.
Web Application Features
One of PHP's oldest features is the ability to make HTML form and cookie data available directly to the
programmer. By default, any form entry creates a global PHP variable of the same name.
In the following example, a user name is retrieved and assigned to a variable. The name is then printed by the
sub-routine "submit.php":
<FORM ACTION="submit.php" METHOD="post">
What's your name? <INPUT NAME="myname" SIZE=3>
<br /> <input type="submit" value=" SUBMIT " name="btn_submit">
</FORM>
submit.php
<?php
print "Hello, $myname!";
?>
Working With Cookies
HTTP cookies (or just cookies) are parcels of text sent by a server to a Web client (usually a browser) and then
sent back unchanged by the client each time it accesses that server.
Each cookie has a name and value. It may also have an expiration time.
Cookies are sent by web server inside the HTTP response before any html content.
Cookies are stored in the client computer.
In PHP, to create cookie, the function setcookie is used. Example:
setcookie ("ck_cnt", $count, time()+3600*24*365); // expires in a year
In PHP, the cookies can be accessed using the super global variable $_COOKIE.
The PHP statement: extract ($_COOKIE);
creates variables with the names of cookies containing their respective values.
HTTP cookies are used for authenticating, session tracking (state maintenance), and maintaining Specific
information about users, such as site preferences or the contents of their electronic shopping carts.
The PHP function setcookie() adds headers to the HTTP response. Since headers must be inserted before the
body, all setcookie() calls must be performed before any body output (usually HTML) is printed.
The following example uses a cookie to store a form value until your browser is terminated.
<?php
if (isset($myname))
{
setcookie("myname", $myname);
}
print <<<_A_
PHP Notes 6 Lakshman Gupta 9:33 AM 10/8/2019
PHP Tutorial
<html>
....
_A_;
....
?>
The following example displays all the cookies releated with the visited site:
<?php
if (!$_COOKIE) { $_COOKIE = $HTTP_COOKIE_VARS; }
foreach ($_COOKIE as $ck => $val)
{ print "<dd>Cookie name: $ck; value: $val<br />\n"; }
?>
Examples:
· Webmail: store and use username.
· Weather Site: store the selected city in a cookie, and next time the site is visited, the weather of the
stored city is automatically displayed.
Built-in Variables
PHP has a number of built-in variables that give you access to your Web server's CGI environment,
form/cookie data and PHP internals. Here are some of the most useful variables:
PHP internal variables
The $GLOBALS and $PHP_SELF variables shown in the table below are specific to PHP:
Variable
Name
Description
$GLOBALS An associative array of all global variables. This is the only variable in PHP that is available
regardless of scope. You can access it anywhere without declaring it as a global first.
$PHP_SELF This is the current script, for example /~ssb/phpinfo.php3.
$_POST An associative array of POST variables.
$_GET An associative array of GET variables.
$_COOKIE An associative array of COOKIE variables.
$_SERVER An associative array of SERVER variables.
CGI / Web server provided variables
The variables listed below are derived from CGI protocols.
Variable Name Description
$DOCUMENT_ROOT Your Web server's base directory with user-visible files.
$REQUEST_METHOD The HTTP method used to access this page, for example GET or POST.
$REQUEST_URI Full local part of the request URL, including parameters.
$SCRIPT_FILENAME File name of the top-level page being executed.
$SCRIPT_NAME Local URI part of the page being executed.
$SERVER_NAME Domain name for the server.
$SERVER_PORT TCP port number the server runs on.
HTTP Request Variables
HTTP Request Variables are derived from their corresponding HTTP headers.
$REMOTE_ADDR IP address of the client (browser) machine
$HTTP_HOST Host name in the browser's "location" field.
$HTTP_USER_AGENT User agent (browser) being used.
$HTTP_REFERER URL of the referring page.
PHP Notes 7 Lakshman Gupta 9:47 AM 10/8/2019
PHP Tutorial
Regular Expressions
Regular expressions, a powerful tool for manipulating text and data, are found in scripting languages, editors,
programming environments, and specialized tools.
Special characters: "/" "-" "^" "." "\" "^" "$" "*" "+" "(" ")"
Equivalent Description or Meaning Examples
/abc/ search for substring "abc"
/[akt]/ search for one of "a", "k" or "t".
/[^akt]/ true if string do not have any one of "a", "k" or "t".
/[0-4]/ /[01234]/ search for one of "0", "1", "2", "3" or "4"
/.../i Case insensitive
* Zero or more /abck*pqr/
+ One or more /abck+pqr/
\d [0-9] Any decimal digit [0123456789]
\D Any character that is not a decimal digit
\w [0-9A-Za-z_] Alphanumerics and underscore
\W Any "non-word" character
\s [ \r\t\n\f] Any Whitespace character
\S Any character that is not a whitespace character
\b At word boundary (at the beginning or end) /\babc/ or /abc\b/ or /\babc\b/
\r Return (CR)
\f Linefeed (LF)
\n New line (CRLF)
\t Tab
/^.../ Starts with /^klm/
/...$/ Ends with /ali$/ /^good$/i
/\d{4}/ 4 digits /\d\d\d\d/ /[A-Z]{3}\d{3}/
/\d{2,4}/ 2 to 4 digits /\d{2} [A-Z]{1,3} \d{2,4}/
(...) Grouping
Regular Expression Functions in PHP
preg_match: Perform a regular expression match
Examples:
// The "i" after the pattern delimiter indicates a case-insensitive search
if (preg_match ("/php/i", "PHP is the web scripting language of choice."))
{
print "A match was found.";
}
else
{
print "A match was not found.";
}
// The \b in the pattern indicates a word boundary, so only the distinct
// word "web" is matched, and not a word partial like "webbing" or "cobweb"
if (preg_match ("/\bweb\b/i", "PHP is the web scripting language of choice."))
{
print "A match was found.";
}
else
{
print "A match was not found.";
}
if (preg_match ("/\bweb\b/i", "PHP is the website scripting language of choice."))
{
print "A match was found.";
}
else
{
print "A match was not found.";
}
preg_replace: Perform a regular expression search and replace
Examples:
$string = 'April 15, 2003';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '${1}1,$3';
print preg_replace($pattern, $replacement, $string); // PHP Notes PHP Tutorial
Database Handling
Communication with MySQL
PHP and MySQL are often referred to as the "dynamic duo" of dynamic Web scripting. PHP and MySQL work
very well together, in addition to the speed and features of each individual tool.
The steps in using MySQL databases in PHP are as follows:
1. Connect to MySQL Server and select database (usually placed in main of the PHP scripts):
$dblink = mysql_connect("localhost", "db_user", "my_password") or die("Could not connect");
mysql_select_db("my_db") or die("Can not select database");
2. Prepare and submit a query:
$query = "select * from person where p_city = '$city'
order by p_lname";
$qno = mysql_query($query) or die("Query error: <b>$query</b><hr />" . mysql_error());
3. Get number of records selected / affected:
$n = mysql_num_rows ($qno); // Get number of records affected.
4. Fetch data from database server:
while ($record = mysql_fetch_assoc($qno))
{
extract($record); // Create variables by table column names
........ // Use these created variables
}
5. Free the query resources:
mysql_free_result ($qno); // Free query result set.
6. Close connection to database server:
mysql_close($dblink); // Close connection.
MySQL Example
The following is a simple example of how to dump the contents of a MySQL table using PHP. The example assumes you have a MySQL user called "db_user" who can connect with password "my_password" from localhost. In the example below, PHP implements the following procedure:
<?php
// Connect and select database:
$dblink = mysql_connect("localhost", "db_user", "my_password")
or die("Could not connect");
mysql_select_db("my_db") or die("Can not select database");
// Perform SQL query:
$query = "select * from user";
$qno = mysql_query($query)
or die("Query failed: $query<hr />" . mysql_error();
$n = mysql_num_rows ($qno); // Get number of records selected/affected.
// Output results in HTML:
print "<table border='1'>\n";
while ($user = mysql_fetch_assoc($qno)) // While a record is retrieved...
{
// Print column headings if first row
if (!$header_printed)
{
print "\t<tr>\n";
$fields = array_keys ($user);PHPNotes 8 Lakshman Gupta 9:48 AM 10/8/2019
PHP Notes 8 Lakshman Gupta 9:37 AM 10/12/2019
PHP Tutorialreset($user); // Rewind for the next foreach
foreach ($fields as $field)
{
print " <th>$field</th>\n"; }
print " </tr>\n";
$header_printed = true;
} // end of print header.
// Output data in the record retrieved.
print "\t<tr>\n";
foreach ($user as $col_value)
{
print "\t\t<td>$col_value</td>\n"
}
print "\t</tr>\n";
}
print "</table>\n";
mysql_free_result($qno); // Free resultset.
mysql_close($dblink); // Close connection.
?>
Communication with Other Databases
Unlike other scripting languages for Web page development, PHP is open-source, cross-platform, and offers excellent connectivity to most of today's common databases including Oracle, Sybase, MySQL, ODBC (and others). PHP also offers integration with various external libraries which enable the developer to do anything from generating PDF documents to parsing XML.
