PHP Tutorial

PHP HOME PHP Intro PHP Install PHP Syntax PHP Comments PHP Variables PHP Echo / Print PHP Data Types PHP Strings PHP Numbers PHP Math PHP Constants PHP Operators PHP If...Else...Elseif PHP Switch PHP Loops PHP Functions PHP Arrays PHP Superglobals PHP RegEx

PHP Forms

PHP Form Handling PHP Form Validation PHP Form Required PHP Form URL/E-mail PHP Form Complete

PHP Advanced

PHP Date and Time PHP Include PHP File Handling PHP File Open/Read PHP File Create/Write PHP File Upload PHP Cookies PHP Sessions PHP Filters PHP Filters Advanced PHP Callback Functions PHP JSON PHP Exceptions


PHP What is OOP PHP Classes/Objects PHP Constructor PHP Destructor PHP Access Modifiers PHP Inheritance PHP Constants PHP Abstract Classes PHP Interfaces PHP Traits PHP Static Methods PHP Static Properties PHP Namespaces PHP Iterables

MySQL Database

MySQL Database MySQL Connect MySQL Create DB MySQL Create Table MySQL Insert Data MySQL Get Last ID MySQL Insert Multiple MySQL Prepared MySQL Select Data MySQL Where MySQL Order By MySQL Delete Data MySQL Update Data MySQL Limit Data


PHP XML Parsers PHP SimpleXML Parser PHP SimpleXML - Get PHP XML Expat PHP XML DOM



PHP Examples

PHP Examples PHP Compiler PHP Quiz PHP Exercises PHP Certificate

PHP Reference

PHP Overview PHP Array PHP Calendar PHP Date PHP Directory PHP Error PHP Exception PHP Filesystem PHP Filter PHP FTP PHP JSON PHP Keywords PHP Libxml PHP Mail PHP Math PHP Misc PHP MySQLi PHP Network PHP Output Control PHP RegEx PHP SimpleXML PHP Stream PHP String PHP Variable Handling PHP XML Parser PHP Zip PHP Timezones

PHP. Lessons for beginners


PHP Regular Expressions

What is a Regular Expression?

A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for.

A regular expression can be a single character, or a more complicated pattern.

Regular expressions can be used to perform all types of text search and text replace operations.


In PHP, regular expressions are strings composed of delimiters, a pattern and optional modifiers.

$exp = "/w3schools/i";

In the example above, / is the delimiter, w3schools is the pattern that is being searched for, and i is a modifier that makes the search case-insensitive.

The delimiter can be any character that is not a letter, number, backslash or space. The most common delimiter is the forward slash (/), but when your pattern contains forward slashes it is convenient to choose other delimiters such as # or ~.

Regular Expression Functions

PHP provides a variety of functions that allow you to use regular expressions. The preg_match(), preg_match_all() and preg_replace() functions are some of the most commonly used ones:

Function Description
preg_match() Returns 1 if the pattern was found in the string and 0 if not
preg_match_all() Returns the number of times the pattern was found in the string, which may also be 0
preg_replace() Returns a new string where matched patterns have been replaced with another string

Using preg_match()

The preg_match() function will tell you whether a string contains matches of a pattern.


Use a regular expression to do a case-insensitive search for "w3schools" in a string:

$str = "Visit W3Schools";
$pattern = "/w3schools/i";
echo preg_match($pattern, $str); // Outputs 1
Try it Yourself »

Using preg_match_all()

The preg_match_all() function will tell you how many matches were found for a pattern in a string.


Use a regular expression to do a case-insensitive count of the number of occurrences of "ain" in a string:

$str = "The rain in SPAIN falls mainly on the plains.";
$pattern = "/ain/i";
echo preg_match_all($pattern, $str); // Outputs 4
Try it Yourself »

Using preg_replace()

The preg_replace() function will replace all the matches of the pattern in a string with another string.


Use a case-insensitive regular expression to replace Microsoft with W3Schools in a string:

$str = "Visit Microsoft!";
$pattern = "/microsoft/i";
echo preg_replace($pattern, "W3Schools", $str); // Outputs "Visit W3Schools!"
Try it Yourself »

Regular Expression Modifiers

Modifiers can change how a search is performed.

Modifier Description
i Performs a case-insensitive search
m Performs a multiline search (patterns that search for the beginning or end of a string will match the beginning or end of each line)
u Enables correct matching of UTF-8 encoded patterns

Regular Expression Patterns

Brackets are used to find a range of characters:

Expression Description
[abc] Find one character from the options between the brackets
[^abc] Find any character NOT between the brackets
[0-9] Find one character from the range 0 to 9


Metacharacters are characters with a special meaning:

Metacharacter Description
| Find a match for any one of the patterns separated by | as in: cat|dog|fish
. Find just one instance of any character
^ Finds a match as the beginning of a string as in: ^Hello
$ Finds a match at the end of the string as in: World$
\d Find a digit
\s Find a whitespace character
\b Find a match at the beginning of a word like this: \bWORD, or at the end of a word like this: WORD\b
\uxxxx Find the Unicode character specified by the hexadecimal number xxxx


Quantifiers define quantities:

Quantifier Description
n+ Matches any string that contains at least one n
n* Matches any string that contains zero or more occurrences of n
n? Matches any string that contains zero or one occurrences of n
n{x} Matches any string that contains a sequence of X n's
n{x,y} Matches any string that contains a sequence of X to Y n's
n{x,} Matches any string that contains a sequence of at least X n's

Note: If your expression needs to search for one of the special characters you can use a backslash ( \ ) to escape them. For example, to search for one or more question marks you can use the following expression: $pattern = '/\?+/';


You can use parentheses ( ) to apply quantifiers to entire patterns. They also can be used to select parts of the pattern to be used as a match.


Use grouping to search for the word "banana" by looking for ba followed by two instances of na:

$str = "Apples and bananas.";
$pattern = "/ba(na){2}/i";
echo preg_match($pattern, $str); // Outputs 1
Try it Yourself »

Complete RegExp Reference

For a complete reference, go to our Complete PHP Regular Expression Reference.

The reference contains descriptions and examples of all Regular Expression functions.