PHP preg_replace "unknown modifier" [duplicate] - php

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Unknown modifier '/' in ...? what is it? [duplicate]
(4 answers)
Closed 9 years ago.
I'm trying to use an array of regular expressions to find and replace within a string in PHP, however I'm getting the error unknown modifier. I'm aware this appears to be a popular issue, however I don't understand how to fix it in my scenario.
Here is my original regex pattern:
{youtube((?!}).)*}
I run the following code against it to escape any characters:
$pattern = '/' . preg_quote($pattern) . '/';
That returns the following:
/\{youtube\(\(\?\!\}\)\.\)\*\}/
However, when I run this pattern through preg_replace I get the following error:
Warning: preg_replace() [function.preg-replace]: Unknown modifier 'y' ...
Any idea what needs to be changed, and at what stage of the code I've show here?
Many thanks
Edit 1
As requested, here is the code I'm using:
$content = "{youtube}omg{/youtube}";
$find = array();
$replace = array();
$find[] = '{youtube((?!}).)*}';
$replace[] = '[embed]http://www.youtube.com/watch?v=';
$find[] = '{/youtube((?!}).)*}';
$replace[] = '[/embed]';
foreach ( $find as $key => $value ) {
$find[$key] = '/' . preg_quote($value) . '/';
}
echo preg_replace($find, $replace, $content);
Here's a live example

Answer 1

You should pass delimiter as second parameter for preg_quote like this:
$find[$key] = '/' . preg_quote ($value, '/') . '/';
Otherwise, delimiter will not be quoted and thus will cause problems.

Answer 2

Simply change your Regex delimiter to something that's not used in the pattern, in this example I used # which works fine.
preg_quote only escapes . \ + * ? [ ^ ] $ ( ) { } = ! < > | : -, so when using a non-escaped character in your pattern, but also as your regex delimiter, it's not going to work as expected. Either change the delimiter as above, or pass it into preg_quote explicitely as part of the preg_quote($str, $delimiter) overload.
$content = "{youtube}omg{/youtube}";
$find = array();
$replace = array();
$find[] = '{youtube((?!}).)*}';
$replace[] = '[embed]http://www.youtube.com/watch?v=';
$find[] = '{/youtube((?!}).)*}';
$replace[] = '[/embed]';
foreach ( $find as $key => $value ) {
$find[$key] = '#' . preg_quote($value) . '#';
}
echo preg_replace($find, $replace, $content);

Answer 3

I may be sat in a hospital waiting room away from a computer, but what you're doing seems to have way over complicated the problem.
If I am to understand this correctly, you want to replace some like this:
{youtube something="maybe"}http://...{/youtube}
With:
[embed]http://...[/embed]
No?
If that's the case the solution is as simple as something along the lines of:
preg_replace('#{(/?)youtube[^}]*}#', '[\1embed]', $content);
The important considerations being the preservation of the open/closed-ness of the tags, and wrapping the regex in something that doesn't conflict quite so much with your target string, in this case, hashes.