PHP: Escaping RegEx-reserved characters - anyone know what's wrong with this?

php regex str-replace
Greg picture Greg · Nov 24, 2009 · Viewed 8k times · Source

I'm trying to escape regex-reserved characters with a backslash (don't ask -- suffice it to say I'm NOT trying to parse HTML :) ) And I'm getting something odd.

$regex_chars = array('[' , '\\' , '^', '$' , '.' , '|' , 
    '?' , '*' , '+' , '(' , ')');  
$regex_chars_escaped = array('\[ ' , '\\\\ ' , '\^ ', '\& ' , 
    '\. ' , '\| ' , '\? ' , '\* ' , '\+ ' , '\( ' , '\)'); 
$escaped_string = str_replace($regex_chars,$regex_chars_escaped,
     implode("",$regex_chars));
echo implode('&nbsp;',$regex_chars) . "<br />";
echo $escaped_string;

Spaces are for clarity. This is the output

[ \ ^ $ . | ? * + ( )
\\ [ \\ \^ \& \. \| \? \* \+ \( \)

So all is good, except for the first part. Where does the "\\" come from and why isn't it "\[" ?

Answer

Bart Kiers picture Bart Kiers · Nov 24, 2009

Why not simply use preg_quote?

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