PHP: Escaping RegEx-reserved characters - anyone know what's wrong with this?
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22-09-2019 - |
Question
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(' ',$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 "\[" ?
Solution
Why not simply use preg_quote?
OTHER TIPS
I believe it's just because of the order you're putting the chars in the array. Try this:
$regex_chars = array('\\' , '[' , '^', '$' , '.' , '|' ,
'?' , '*' , '+' , '(' , ')');
$regex_chars_escaped = array( '\\\\ ' ,'\[ ', '\^ ', '\& ' ,
'\. ' , '\| ' , '\? ' , '\* ' , '\+ ' , '\( ' , '\)');
And you should get the expected output. Check the 'potential gotchas' section in the str_replace function spec
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