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PHP preg_replace_callback_array() Function

❮ PHP RegExp Reference

Example

Show how many letters or digits are found in each word in a sentence:

<?php
function countLetters($matches) {
  return $matches[0] . '[' . strlen($matches[0]) . 'letter]';
}

function countDigits($matches) {
  return $matches[0] . '[' . strlen($matches[0]) . 'digit]';
}

$input = "There are 365 days in a year.";
$patterns = [
  '/\b[a-z]+\b/i' => 'countLetters',
  '/\b[0-9]+\b/' => 'countDigits'
];
$result = preg_replace_callback_array($patterns, $input);
echo $result;
?>
Try it Yourself »

Definition and Usage

The preg_replace_callback_array() function returns a string or an array of strings in which matches of a set of regular expressions are replaced with the return value of a callback function.

Note: For each string, the function evaluates the patterns in the order that they are given. The result of evaluating the first pattern on the string is used as the input string for the second pattern and so on. This can lead to unexpected behaviour.


Syntax

preg_replace_callback_array(patterns, input, limit, count)

Parameter Values

Parameter Description
pattern Required. An associative array which associates regular expression patterns to callback functions.

The callback functions have one parameter which is an array of matches.The first element in the array contains the match for the whole expression while the remaining elements have matches for each of the groups in the expression.
input Required. The string or array of strings in which replacements are being performed
limit Optional. Defaults to -1, meaning unlimited. Sets a limit to how many replacements can be done in each string
count Optional. After the function has executed, this variable will contain a number indicating how many replacements were performed

Technical Details

Return Value: Returns a string or an array of strings resulting from applying the replacements to the input string or strings
PHP Version: 7+

More Examples

Example

This example illustrates the potentially unexpected effects of the patterns being evaluated in sequence. First, the countLetters replacement adds "[4letter]" to "days" and, after that replacement has been performed, the countDigits replacement finds the "4" in "4letter" and adds "[1digit]" to that:

<?php
function countLetters($matches) {
  return $matches[0] . '[' . strlen($matches[0]) . 'letter]';
}

function countDigits($matches) {
  return $matches[0] . '[' . strlen($matches[0]) . 'digit]';
}

$input = "365 days";
$patterns = [
  '/[a-z]+/i' => 'countLetters',
  '/[0-9]+/' => 'countDigits'
];
$result = preg_replace_callback_array($patterns, $input);
echo $result;
?>
Try it Yourself »

❮ PHP RegExp Reference