How can conditional matching be implemented in PHP regular expressions to only match patterns if certain conditions are met, such as the absence of a specific character after a match?

To implement conditional matching in PHP regular expressions to only match patterns if certain conditions are met, such as the absence of a specific character after a match, you can use a negative lookahead assertion. This allows you to specify a pattern that should not be present after the initial match. By using this technique, you can ensure that the pattern is only matched when the specified condition is satisfied. 

$string = "example123";
$pattern = '/\d(?!a)/'; // Match a digit only if the next character is not 'a'

if (preg_match($pattern, $string)) {
    echo "Pattern matched successfully!";
} else {
    echo "Pattern not found or condition not met.";
}

Keywords

PHP regular expressions conditional matching negative lookahead character absence

Related Questions