php中Warning: preg_match_all(): Compilation failed: lookbehind assertion
Release： 2016-07-25 08:46:43
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Today when I was testing the code related to looking around in regular expressions, I found an error
The error message is as follows:
Warning: preg_match_all(): Compilation failed: lookbehind assertion is not fixed length at offset
The code is as follows:
- $str='
info strong';
- preg_match_all('/(?<=<(w+)[ ^>]*>).*(?=)/',$str,$match);
- var_dump($match);
Execute the above code An error will be reported. After checking online, it is said that reverse lookaround in PHP (including reverse positive lookaround?<=exp, reverse negative lookaround?
Change the above code to:
- $str='
info strong';
- preg_match_all('/(?<=< (w)>).*(?=)/',$str,$match);
- var_dump($match);
But this can only match b Strong content in tags
Actually, you don’t need to look around to match, you can directly use grouping to capture the content. You just need to filter the returned results
- $str='
info strong';
- preg_match_all('/(<(w+)[^>]*>)(.*)()/',$str,$match);
- print_r( $match[3]);//Array ( [0] => info [1] => strong )
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