How can the use of Unicode characters impact the effectiveness of regular expressions in PHP?

When working with Unicode characters in PHP regular expressions, it's important to use the "u" modifier to ensure proper handling of multibyte characters. Without this modifier, regular expressions may not correctly match Unicode characters, leading to unexpected results or errors. By including the "u" modifier, PHP will interpret the pattern and subject strings as UTF-8, allowing for accurate matching of Unicode characters. 

$pattern = '/\p{L}/u'; // Match any Unicode letter
$string = 'Привет, 你好, Hello';

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

Keywords

Unicode characters regular expressions PHP multibyte strings character encoding

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