Php regular expressions tutorial for web developer

In php to find any text, characters and matching as your own patterns or if anybody want there custom patterns, its all are done by using PHP Regular Expressions. Like searching , it can also does replacing words. The regular expressions tools are very important tools for web developers. It is mostly use for searchiing any text or content.

Hide Example Show Example

Regular Expressions symbol

To learn Php Regular expressions, need to learn about the basic symbol of regular expressions which are used in regular expressions. There are some symbols which must learn to complete the regular expressions. These symbols of regular expressions are listed below.

Pattern	Description
^	This( ^ ) symbol denoted started with the pattern.
$	This( $ ) symbol denoted ended with the pattern.
.	This stop ( . ) symbol denoted a single character .
?	This ( ? ) symbol denoted the precedding pattern zero or one
+	This ( + ) symbol denoted the precedding pattern one or more.
*	This ( ? ) symbol denoted the precedding pattern zero or more
|	This symbol ( | ) works like Boolean OR
-	This ( - ) symbol denoted a range of elements
()	This ( () ) symbol denoted the groups of patterns.
[]	This ( [] ) symbol denoted the a single pattern between this third brackets..
{min,}	This denoted to minimum characters to more characterrs
{,max}	This denoted to maximum characters
{min,max}	This denoted to minimum to maximum characters.
/i	This denoted to insensitive case characters
[Bangladesh]
\d	Matches only single digits
\D	Matching only no digits.
\w	Matches any alpha numeric character including underscore (_)
\W	Matches any non alpha numeric character excluding the underscore character
\s	Matches whitespace character

Regular Expressions symbol uses

After learning about these symbols, now you need to learn how to use these symbols and what effects. Regular expression symbols takes more effect if any symbol changes. So need to clear and ovserve it what effects take. Let's started

Pattern	Match Pattern	Not match pattern	Description
Bangladesh	Bangaldesh	Bangladesh1, Others , Dhaka	Only contains the word "Bangladesh"
^(Bangladesh)	Bangladesh is a wonderful country.	In the world, Bangladesh is situated at the southern part of Asia	Staring any sentence with word "Bangladesh"
(Bangladesh)$	We like Bangladesh.	Bangladesh is a wonderful country.	Ending with the word "Bangladesh"
^(Bangladesh)$	Bangladesh is like "Bangladesh"	Bangladesh is a wonderful country. We like Bangladesh	Starting and Ending with the word "Bangladesh"
(Bangladesh)/i	bangladesh,BanGlAdeSh	Bangladesh1	Only contain the word "Banglaadesh" with capital or samll letter
Banglades(h)*	Bangladeshhhh, Bangladesh	Banglades	Contains the letters one or more after "Banglades"
Banglades(h)+	Bangladesh, Banglades, Bangladeshh	Bangla, Banglladesh	Contains the letter zero or more time after "Banglades"
Banglades(h)?	Bangladesh, Banglades	Bangladeshhh	Contains the letter zero or one time after "Banglades"
Banglades(h){1}	Bangladesh	Bangladeshh,Bangladeh1	Contains the letter one time after "Banglades" .
Banglades(h){2,}	Bangladeshh, Bangladeshhh	Bangladesh	Contains the letter 2 or more time after "Banglades"
Bangldes(h){1,6}	Bangladesh,	Banglades, Bangladeshhhhhhhhhhhhh	Contains the letter onr or more 6 times after "Banglades"
^{5}$	tajbi	taj, taj1 , tajbir	Any five characters combination letters, symbols or digit
Bangla(desh)*			Contains "desh" one or more times after "Bangla"
Bangladesh|Dhaka			Contains Bangladesh OR Dhaka
[Bangladesh]			Combination of letters within braces
[a-z]	a, az, ab, abc	Ab, AB	Contains any small letters
[a-zA-Z]	ab, ABCd	ab1, abc16	Contains any small and capital letter
[a-zA-Z0-9]	ab12, AbcD2	ab@,sD10!	Any digits and all capital and small letters
[a-zA-Z0-9._-]	abcd.-	adcd@	Any digits,all capital and small letters, dot, underscore and hyphen
^[a-zA-Z0-9_]{1,}$	avcd	@123456	Contains any digits,all capital and small letters, dot, underscore and hyphen with minimum 1 characters
^[a-zA-Z0-9_]{5,10}$	abcdefg, bangla	ban	Contains any digits,all capital and small letters, dot, underscore and hyphen with 5 - 10 characters
([wx])([yz])	wy,wz,xy,yz	wxyz	Combinations of wx and yz. Like wy,wz,xy,yz
([A-Z]{3}|[0-9]{4})	dbc, 1234	abcd, 012345	Three capital letters or any 4 digits
[a-z]+	al	AB	Any small letters contains 1 or more letters
[^(a-z)]	abul, bangle	Abul, Bnagle	Satrt with any small letter
[^(az)]	abul, ziko	Abul, liko	Start with small letters a and z

Regular Expressions functions

To finding any text or any words Regular epressions is most important. But how to use it in php. In PHP there has some functions which are used for reular expressions. All of the functions, some are case sensitive checking and some are case insensitive.

Function	Description
preg_match()	The preg_match() function searches string for pattern, returning true if pattern exists, and false otherwise.
preg_replace	The preg_replace() function operates just like ereg_replace(), except that regular expressions can be used in the pattern and replacement input parameters.
eregi()	Case insensitive regular expression match
eregi_replace	Replace regular expression case insensitive
ereg()	Case sensitive regular expression match
ereg_replace	Replace regular expression
preg_split()	The preg_split() function operates exactly like split(), except that regular expressions are accepted as input parameters for pattern.
preg_grep()	The preg_grep() function searches all elements of input_array, returning all elements matching the regexp pattern.
preg_ quote()	Quote regular expression characters
preg_match_all()	The preg_match_all() function matches all occurrences of pattern in string.
stristr()

Regular expression check using php Functions

Searching or matching word using regular expression in php is a easy task.

Example : Check a word like "tajbir"

<?php
 $pattern = "/^(tajbir)$/";
 $txt = "tajbir";
  
 if (preg_match($pattern,$txt)) 
  echo "Found";
 else 
  echo "Not Found";
?>

//Output:
//Found

Searching the limited chareacters.
Example : search a word which contains only two to five characters.

<?php 
 $pattern = "/^[a-zA-Z]{2,5}$/";
 $txt = "taj";
  
 if (preg_match($pattern,$txt)) 
  echo "Found";
 else 
  echo "Not Found";
?>

//Output:
//Found

Searching chareacters and specific symbols also.
Example : A word that contains only letters and dot sign

<?php  
 $pattern = '/^[a-zA-Z.]{1,}$/';
    $txt= "Bangla.desh-";
     
    if (preg_match($pattern,$txt)) 
  echo "Found";
    else 
  echo "Not Found";
?>

//Output:
//Not Found

All characters ,digits and and combination of symbols search.
Example : A word that contains combinations 4 to 20 lettres,digits,hyphen,undescore, dot or any of the one.

<?php  
 $pattern = '/^[a-zA-Z0-9_.-]{4,20}$/';
    $txt= "Bangla.desh-";
     
    if (preg_match($pattern,$TXT)) 
  echo "Found";
    else 
  echo "Not Found";
?>

//Output:
//Found

Some common PHP regular expressions for web developers

Some regular and common used php Regular Expressions are mentioned given below.

Check any email using regular expressions by preg_match() in php

<?php
 $pattern = "/^[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+\.[a-zA-Z.]{2,5}$/";
 $email = "tajbir@yahoo.com";
  
 if (preg_match($pattern,$email)) 
  echo "Found";
 else 
  echo "Not Found";
?>
 

Check any email using regular expressions by eregi() in php

 <?php   
 $pattern = "^[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+\.[a-zA-Z.]{2,5}$";
    $email = "tajbir@yahoo.com";
     
    if (eregi($pattern,$email))
  echo "Found";
    else
  echo "Not Found";
?>
 

 <?php
$url = "http://komunitasweb.com/";
if (preg_match('/^(http|https|ftp)://([A-Z0-9][A-Z0-9_-]*(?:.[A-Z0-9][A-Z0-9_-]*)+):?(d+)?/?/i', $url)) {
    echo "Your url is ok.";
} else {
    echo "Wrong url.";
}  
 ?>
 

Wordpress title search using regular expressions

<?php
 $title  = get_the_title();
 $keys= explode(" ",$s);
 $title  = preg_replace('/('.implode('|', $keys) .')/iu','<strong class="search-excerpt">\0</strong>',
  $title);
?>
 

Get all images from a html document

<?php
$images = array();
preg_match_all('/(img|src)=("|')[^"'>]+/i', $data, $media);
unset($data);
$data=preg_replace('/(img|src)("|'|="|=')(.*)/i',"$3",$media[0]);
foreach($data as $url)
{
 $info = pathinfo($url);
 if (isset($info['extension']))
 {
  if (($info['extension'] == 'jpg') ||
  ($info['extension'] == 'jpeg') ||
  ($info['extension'] == 'gif') ||
  ($info['extension'] == 'png'))
  array_push($images, $url);
 }
}
?>

Matching HEXA decimal values

 $string = "#555555";
if (preg_match('/^#(?:(?:[a-fd]{3}){1,2})$/i', $string)) {
echo "example 6 successful.";
}
 

Find page title tag

<?php  
 $fp = fopen("http://www.catswhocode.com/blog","r");
 while (!feof($fp) ){
  $page .= fgets($fp, 4096);
 }

 $titre = eregi("",$page,$regs);
 echo $regs[1];
 fclose($fp);
?>

Matching aany XML/HTML tag

<?php
 function get_tag( $tag, $xml ) {
  $tag = preg_quote($tag);
  preg_match_all('{<'.$tag.'[^>]*>(.*?).'}',
                   $xml,
                   $matches,
                   PREG_PATTERN_ORDER);

  return $matches[1];
}
?>

Validating a url

<?php
 $pattern = "/^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \?=.-]*)*\/?$/";
 $url = "http://www.taslimblogger.com";
  
 if (preg_match($pattern,$emurl)) echo "Found";
 else echo "Not Found";
?>
 

Validate US number

<?php

 /^(\+\d)*\s*(\(\d{3}\)\s*)*\d{3}(-{0,1}|\s{0,1})\d{2}(-{0,1}|\s{0,1})\d{2}$/
?>

Check the password is weak or strong if a password is strong
Weak passwords are one of the quickest ways to get hacked. The following regexp will make sure that:

Passwords will contain at least (1) upper case letter
Passwords will contain at least (1) lower case letter
Passwords will contain at least (1) number or special character
Passwords will contain at least (8) characters in
Password maximum length should not be arbitrarily

<?php
 (?=^.{8,}$)((?=.*\d)|(?=.*\W+))(?![.\n])(?=.*[A-Z])(?=.*[a-z]).*$
?>

Get the code between php tag

<?php
 <\?[php]*([^\?>]*)\?>
?>

Grab unclosed img tags As you probably know, the xhtml standard requires all tags to be properly closed. This regular expression will search for unclosed img tags. It could be easily modified to grab any other unclosed html tags.

<?php
 <img([^>]+)(\s*[^\/])>
 ?>

This regex will find CSS attributes, such as background:red; or padding-left:25px;.

<?php
 \s(?[a-zA-Z-]+)\s[:]{1}\s*(?[a-zA-Z0-9\s.#]+)[;]{1}
 ?>

This all functions are used to secure php data searching. This tools help the web developers to easliy find anything in webpages.