What are some common pitfalls to avoid when using preg_match_all in PHP?

One common pitfall to avoid when using preg_match_all in PHP is not properly escaping special characters in the regex pattern. This can lead to unexpected results or errors in the matching process. To solve this issue, it is important to use the preg_quote function to escape any special characters in the pattern before passing it to preg_match_all.

// Incorrect usage without escaping special characters
$pattern = '/[a-z]+/';
$string = 'Hello World';
preg_match_all($pattern, $string, $matches);

// Corrected code with escaping special characters
$pattern = '/'.preg_quote('[a-z]+').'/';
$string = 'Hello World';
preg_match_all($pattern, $string, $matches);