What potential pitfalls should be considered when using regular expressions to manipulate strings in PHP?

One potential pitfall when using regular expressions to manipulate strings in PHP is the risk of introducing vulnerabilities such as regex injection. To mitigate this risk, it is important to properly sanitize user input before using it in a regular expression. This can be done by using functions like preg_quote() to escape special characters in the input. 

// Sanitize user input before using it in a regular expression
$user_input = $_POST['user_input'];
$sanitized_input = preg_quote($user_input);

// Use the sanitized input in the regular expression
$pattern = '/^' . $sanitized_input . '$/';
$string = 'example string';

if (preg_match($pattern, $string)) {
    echo 'Match found!';
} else {
    echo 'No match found.';
}

Keywords

regular expressions strings manipulation PHP pitfalls

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