PHP Regular Expression Functions

PHP Regular Expression Functions

PHP provides a variety of functions that allow you to use regular expressions.

Some common regexp functions are:

• 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
• preg_replace() - Returns a new string where the matched patterns is replaced with another string
• preg_split() - Splits a string into an array using matches of a regular expression as separators
• preg_grep() - Returns an array containing only elements from the input that match the given pattern

PHP preg_match() Function

Thepreg_match() function returns 1 if the pattern was found in the string, and 0 if not.

$str = "Visit W3Schools";$pattern = "/w3schools/i";echo preg_match($pattern, $str);

PHP preg_match_all() Function

Thepreg_match_all() function returns how many matches were found for a pattern in astring.

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

PHP preg_replace() Function

Thepreg_replace() function replaces all the matches of the pattern in a string withanother string.

$str = "Visit Microsoft!";$pattern = "/microsoft/i";echo preg_replace($pattern, "W3Schools", $str);

PHP preg_split() Function

Thepreg_split() function splits a string into an array using matches of a regular expression as separators.

$str = "This is a text";$pattern = "/[\s:]/";$components = preg_split($pattern, $str);print_r($components);

PHP preg_grep() Function

Thepreg_grep() function returns an array containing only elements from the input that match the given pattern.

$input = ["Red","Pink","Green","Blue","Purple"];$result = preg_grep("/^p/i", $input);print_r($result);

Thepreg_grep() function also has a third parameterPREG_GREP_INVERT which will invert the result and returns an array containing only elements outside the input that match the given pattern.

$input = ["Red","Pink","Green","Blue","Purple"];$result = preg_grep("/^p/i", $input, PREG_GREP_INVERT);print_r($result);

Grouping

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

$str = "Apples and bananas.";$pattern = "/ba(na){2}/i";echo preg_match($pattern, $str);

Complete RegExp Reference

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

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