What role does escaping special characters play in ensuring the validity of regular expressions in PHP?

Escaping special characters in regular expressions in PHP is crucial to ensure the validity of the regex pattern. Special characters like parentheses, square brackets, and backslashes have special meanings in regular expressions, so escaping them allows the regex engine to interpret them as literal characters. This prevents any unintended behavior or errors in the regex pattern.

$pattern = "/^(\d+)\s\+\s(\d+)\s=\s(\d+)$/";
$escaped_pattern = preg_quote($pattern, '/');