PHP PCRE error preg_replace

Answer 1

It seems you want to escape special regex characters. This function already exists and is called preg_quote().

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You get the error, because you don't escape \ properly:

TI - Yeah U Know \[OFFCIAL VIDEO\] \[TAKERS\] \[w\LYRICS\]
//                   this is not escaped   ------^

and \L has special meaning in Perl regular expression:

\L Lowercase until \E

but is not supported in PHP's PCRE (Perl Differences):

The following Perl escape sequences are not supported: \l, \u, \L, \U. In fact these are implemented by Perl's general string-handling and are not part of its pattern matching engine.

Update:

Obviously, you cannot use the escaped version as value and as pattern, because in the pattern \[ will be treated as [ and but in the value \[ is taken literally. You have to store the escaped string in a new variable:

$var = "TI - Yeah U Know [OFFCIAL VIDEO] [TAKERS] [w\LYRICS]";

$escaped = preg_quote($var);
echo $escaped . PHP_EOL;
// prints "TI - Yeah U Know \[OFFCIAL VIDEO\] \[TAKERS\] \[w\\LYRICS\]"
$var = preg_replace('#' . $escaped . '#isU', 'test', $var);
echo $var;
// prints test

or easier:

$var = preg_replace('#' . preg_quote($var) . '#isU', 'test', $var);

Side note: If you really wanted to match \[ in a string, the regular expression would be \\\\\[. You see, it can get quite ugly.