PHP preg_replace_callback_array() Function
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