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PHP preg_replace_callback() Function

❮ PHP RegExp Reference


Count letters in all of the words in a sentence:

function countLetters($matches) {
  return $matches[0] . '(' . strlen($matches[0]) . ')';

$input = "Welcome to W3Schools.com!";
$pattern = '/[a-z0-9\.]+/i';
$result = preg_replace_callback($pattern, 'countLetters', $input);
echo $result;
Try it Yourself »

Definition and Usage

The preg_replace_callback() function, given an expression and a callback, returns a string where all matches of the expression are replaced with the substring returned by the callback function.


preg_replace_callback(pattern, callback, input, limit, count)

Parameter Values

Parameter Description
pattern Required. A regular expression or array of regular expressions indicating what to search for
replacements Required. A callback function which returns the replacement.

The callback function has one parameter containing 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: 4.0.5+
Changelog: PHP 5.1.0 - The count parameter was added

❮ PHP RegExp Reference