Preg_replace_callback

(PHP 4 >= 4.0.5, PHP 5)

Note that it is in most cases much more efficient to use pregreplacecallback, with a named function or an anonymous function created with createfunction, instead of the /e modifier. When pregreplace is called with the /e modifier, the interpreter must parse the replacement string into PHP code once for every replacement made, while. The e modifier is short for eval. It performs a back reference substitution, then executes the replacement string as PHP, then performs the substitution using the returned value. Description mixed pregreplacecallback ( mixed pattern, callback callback, mixed subject , int limit , int &count ). The behavior of this function is almost identical to pregreplace, except for the fact that instead of replacement parameter, one should specify a callback that will be called and passed an array of matched elements in the subject string. Mar 13, 2021 Pregreplacecallbackarray function in PHP 7 represents a regular expression and replaces the use of callbacks. This function returns a string or an array of strings to match a set of regular expressions and replaces them using a callback function. Syntax pregreplacecallbackarray(patterns, input, limit, count) Parameter Values.

preg_replace_callback -- Perform a regular expression search and replace using a callback

Description

mixed preg_replace_callback ( mixed pattern, callback callback, mixed subject [, int limit [, int &count]] )

The behavior of this function is almost identical to preg_replace(), except for the fact that instead of replacement parameter, one should specify a callback that will be called and passed an array of matched elements in the subject string. The callback should return the replacement string. See preg_replace() for description of other parameters.

Example 1. preg_replace_callback() example

<?php
// this text was used in 2002
// we want to get this up to date for 2003
$text = 'April fools day is 04/01/2002n';
$text.= 'Last christmas was 12/24/2001n';
// the callback function
function next_year($matches)
{
// as usual: $matches[0] is the complete match
// $matches[1] the match for the first subpattern
// enclosed in '(..)' and so on
return $matches[1].($matches[2]+1);
}
echo
preg_replace_callback(
' (d{2}/d{2}/)(d{4}) ',
'next_year',
$text);
// result is:
// April fools day is 04/01/2003
// Last christmas was 12/24/2002
?>
Argument

You'll often need the callback function for a preg_replace_callback() in just one place. In this case you can use create_function() to declare an anonymous function as callback within the call to preg_replace_callback(). By doing it this way you have all information for the call in one place and do not clutter the function namespace with a callback functions name not used anywhere else.

Example 2. preg_replace_callback() and create_function()

<?php
/* a unix-style command line filter to convert uppercase
* letters at the beginning of paragraphs to lowercase */
$fp = fopen('php://stdin', 'r') or die('can't read stdin');
while (!
feof($fp)) {
$line = fgets($fp);
$line = preg_replace_callback(
' <p>s*w ',
create_function(
// single quotes are essential here,
// or alternative escape all $ as $
'$matches',
'return strtolower($matches[0]);'
),
$line
);
echo
$line;
}
fclose($fp);
?>

Example 3. preg_replace_callback() using recursive structure to handle encapsulated BB code

<?php
$input
= 'plain [indent] deep [indent] deeper [/indent] deep [/indent] plain';
function
parseTagsRecursive($input)
{
$regex = '#[indent]((?:[^[] [(?!/?indent]) (?R))+)[/indent]#';
if (
is_array($input)) {
$input = '<div>'.$input[1].'</div>';
}
return
preg_replace_callback($regex, 'parseTagsRecursive', $input);
}
$output = parseTagsRecursive($input);
echo
$output;
?>

Preg_replace_callback Multiple Matches

Note: count parameter is available since PHP 5.1.0.

See also preg_replace(), create_function(), and information about the callback type.

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Preg_replace_callback_array

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