Question

Need Some Help With Regex:

I want to replace

[url=http://youtube.com]YouTube.com[/url]

with

<a href="http://youtube.com">YouTube.com</a>

the regex

preg_replace("/[url=(.*?)](.*?)[/url]/is", '<a href="$1">$2</a>', $text);

why does this give me:

Warning: preg_replace() [function.preg-replace]: Unknown modifier ‘r’ in C:\Programa\wamp\www\func.php on line 18

Answer 1

You should escape special characters in your regular expression:

preg_replace('/\[url=(.*?)](.*?)\[\/url]/is', '<a href="$1">$2</a>', $text);

I have escaped the [ characters (they specify the start of a character class) and the / character (it specifies the boundaries of the regular expression.)

Alternatively (for the / character) you can use another boundary character:

preg_replace('#\[url=(.*?)](.*?)\[/url]#is', '<a href="$1">$2</a>', $text);

You still have to escape the [ characters, though.