Question

I’ve made some progress with my regex that I’m using to extract attributes from pseudo-xml-tags, but then I got ambitous and wanted to correctly handle quoted attributes (with quotes being optional):

regex

~\{language\s*=\s*(P?<quote>[\"\']*)(?P<att>.*?)(?P=quote)\s*/\}~

(this is the output of the var that is used as arg in preg_match, so ‘sensible things’ such as \” were created with chr(92) . chr(34) beforehand…)

input

kjkjkjkjkjkj{language= 'DE' /}xxxxlxlxlxlllllk

extracts 'DE‘ when testing with RegexBuddy. But PHPs preg_match issues a warning: Warning: preg_match(): Compilation failed: reference to non-existent subpattern at offset 56.

What’s the problem? I thought “quote” was assigned before…

Here’s the complete program, just in case I have a PHP-error somewhere:

<?php


$QQ=chr(92) . chr(34);
$delimeters = "{}";
$del0 = preg_quote($delimeters{0});
$del1 = preg_quote($delimeters{1});
$tag="language";

$string="fdfdfdfdf{language=1}testhgg";

$preg1 = "|" . $del0 . $tag . "[^" . $del1 . "]*" . $del1 . "(.*?)" . $del0 . "/" . $tag . $del1 . "|";
$preg2 = "~" . $del0 . $tag . "\s*=\s*(?P<" . "quote>[" . $QQ . "\']*)(?P<att>.*?)(?P=quote)\s*/" . $del1 . "~";

$match=array();
preg_match($preg1,$string,$match);
echo "<br>match1:<pre>";var_dump($match);echo"</pre>";

$match=array();
preg_match($preg2,$string,$match);
echo "<br>match2:<pre>";var_dump($match);echo"</pre>";

?>

Answer 1

Your named subpattern is formatted incorrectly.

(P?<quote>[\"\']*)

should be

(?P<quote>[\"\']*)

See http://php.net/manual/en/regexp.reference.subpatterns.php