What are some common pitfalls or challenges faced when trying to implement regular expressions in PHP for text processing tasks?

One common pitfall when using regular expressions in PHP for text processing tasks is not properly escaping special characters, which can lead to unexpected behavior or errors. To avoid this issue, make sure to use the PHP function `preg_quote()` to escape any special characters in your regular expression pattern.

$pattern = '/^http:\/\/www\..+\.com$/';
$escaped_pattern = preg_quote($pattern, '/');