stripping enclosed text from PHP code

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Hi,

I am writing on a script that parses a PHP script and finds all function calls 
to check, if these functions exist. To do this, I needed a function that would 
strip out all text, which is enclosed in apostrophes or quotation marks. This 
is somewhat tricky, as the script needs to be aware of what really is an 
enclosed text and what is PHP code. Apostrophes in quotation mark enclosed text 
should be ignored and quotation marks in apostrophe enclosed text should be 
ignored, as well. Similarly, escaped apostrophes in apostrophe enclosed text 
and escaped quotation marks in quotation mark enclosed text should be ignored. 

The following function uses preg_match to do this job. 

<?

function stripstrings($text) {
	while (preg_match("/^(.*)(?<!\\\)('|\")(.*)$/", $text, $matches)) {

		$front = $matches[1];
		$lim = $matches[2];
		$tail = $matches[3];

		while (preg_match("/^(.*)(?<!\\\)('|\")(.*)$/", $front, $matches)) {
			$front = $matches[1];
			$tail = $matches[3] . $lim . $tail;
			$lim = $matches[2];
		}

		if (!preg_match("/^(.*)(?<!\\\)$lim(.*)$/", $tail, $matches))
			break;

		$string = $matches[1];
		$tail = $matches[2];
		while (preg_match("/^(.*)(?<!\\\)$lim(.*)$/", $string, $matches)) {
			$string = $matches[1];
			$tail = $matches[2] . $lim . $tail;
		}

		$text = $front . $tail;
	}

	return($text);
}

?>

I noticed that this function is very slow, in particular because 

preg_match("/^(.*)some_string(.*)$/", $text, $matches);

always seems to find the *last* occurrence of some_string and not the *first* 
(I would need the first). There is certainly a way to write another version 
where one looks at every single character when going through $text, but this 
would make the code much more complex.

I wonder, if there is a faster *and* simple way to do the same thing. 

Is there btw a script freely available, which can parse PHP code and check for 
errors ?

Any help is highly appreciated.

Winfried

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