The preg_match Function

The preg_match function searches a string for matches with a regular expression. The first parameter accepts the regular expression pattern, the second - the string to search, the third (optional) - an array to save found matches, the fourth (optional) - flags, the fifth (optional) - the offset of the start of the search.

Syntax

phppreg_match(pattern, subject, [matches], [flags], [offset]);

Flags

Example

Let's check if the string contains digits:

php<?php
  $res = preg_match('/\d+/', 'abc123');
  echo $res;
?>

Code execution result:

php1

Example

Let's extract all digits from the string into an array:

php<?php
  preg_match('/\d+/', 'abc123', $matches);
  var_dump($matches);
?>

Code execution result:

php[0 => '123']

Example

Using named groups in a regular expression:

php<?php
  preg_match('/(?P<name>\w+)\s+(?P<age>\d+)/', 'John 25', $matches);
  var_dump($matches);
?>

Code execution result:

php[
  0 => 'John 25',
  'name' => 'John',
  1 => 'John',
  'age' => '25',
  2 => '25'
]

Example

Using the PREG_OFFSET_CAPTURE flag to get the match position:

php<?php
  preg_match('/\d+/', 'abc123', $matches, PREG_OFFSET_CAPTURE);
  var_dump($matches);
?>

Code execution result:

php[
  0 => [
    0 => '123',
    1 => 3
  ]
]

Example

Search with an offset specified:

php<?php
  preg_match('/\d+/', '123abc456', $matches, 0, 3);
  var_dump($matches);
?>

Code execution result:

php[0 => '456']

Example

Checking the validity of an email address:

php<?php
  $email = 'test@example.com';
  $res = preg_match('/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/', $email);
  echo $res ? 'Valid' : 'Invalid';
?>

Code execution result:

php'Valid'

See Also