preg_quote
The last example -nested BBCode- has a problem and won't work
it should be
<?php
$regex = '#\[indent]((?:[^\[]|\[(?!/?indent])|(?R))+)\[/indent]#';
?>
([ should be escaped to be \[)
--
a nicer regex i used in a BBCode parser (BBEngine http://www.phpclasses.org/browse/package/4829.html)
This one Captures Tag Arguments ,Empty tags and
also uses ?> for performance , wrapped in a simple function for templating (ofcourse it's one line but note's line size is limited :) )
<?php
/**
* A Template for the recursive tags matcher RE
* it generates it for a given tag ,open bracket and closing one
* $O & $C must be pre-escaped from #'s
* @param String $tag Tag to be parsed recursively
* @param String $O Opeening brackets of tag
* @param String $C Closing brackets of tag
*/
public function Recursive_RE_Generator($tag,$O,$C)
{
$re="#{$O}({$tag}.*?){$C}((?>{$O}(?!/?{$tag}[^{$O}]*?{$C})|
[^{$O}]|(?R))*){$O}/{$tag}{$C}#is";
return $re;
}
?>
preg_replace_callback
(PHP 4 >= 4.0.5, PHP 5)
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 .
Parameters
- pattern
-
The pattern to search for. It can be either a string or an array with strings.
- callback
-
A callback that will be called and passed an array of matched elements in the subject string. The callback should return the replacement string.
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 function's name not used anywhere else.
Example #1 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);
?> - subject
-
The string or an array with strings to search and replace.
- limit
-
The maximum possible replacements for each pattern in each subject string. Defaults to -1 (no limit).
- count
-
If specified, this variable will be filled with the number of replacements done.
Return Values
preg_replace_callback() returns an array if the subject parameter is an array, or a string otherwise.
If matches are found, the new subject will be returned, otherwise subject will be returned unchanged.
ChangeLog
| Version | Description |
|---|---|
| 5.1.0 | The count parameter was added |
Examples
Example #2 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 04/01/2002\n";
$text.= "Last christmas was 12/24/2001\n";
// the callback function
function next_year($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);
?>
The above example will output:
April fools day is 04/01/2003 Last christmas was 12/24/2002
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)) {
$input = '<div style="margin-left: 10px">'.$input[1].'</div>';
}
return preg_replace_callback($regex, 'parseTagsRecursive', $input);
}
$output = parseTagsRecursive($input);
echo $output;
?>
add a note
User Contributed Notespreg_replace_callback
harrrrpo at gmail dot com
19-Sep-2008 03:59
19-Sep-2008 03:59
nene at triin dot net
20-May-2008 06:14
20-May-2008 06:14
The first example is bad, because it creates function for every line it processes. When the file has many lines, you could easily run out of memory. The code should be changed so, that create_function() is used outside of loop.
Sjon at hortensius dot net
24-Jun-2007 07:56
24-Jun-2007 07:56
preg_replace_callback returns NULL when pcre.backtrack_limit is reached; this sometimes occurs faster then you might expect. No error is raised either; so don't forget to check for NULL yourself
matt at mattsoft dot net
26-Apr-2006 05:16
26-Apr-2006 05:16
it is much better on preformance and better practice to use the preg_replace_callback function instead of preg_replace with the e modifier.
function a($text){return($text);}
// 2.76 seconds to run 50000 times
preg_replace("/\{(.*?)\}/e","a('\\1','\\2','\\3',\$b)",$a);
// 0.97 seconds to run 50000 times
preg_replace_callback("/\{(.*?)\}/s","a",$a);