How can PHP developers ensure that regular expressions accurately match specific characters within a string, without being affected by PHP's own escape sequences?

To ensure that regular expressions accurately match specific characters within a string without being affected by PHP's escape sequences, developers can use single quotes instead of double quotes when defining the regular expression pattern. This prevents PHP from interpreting escape sequences within the pattern, allowing the regex engine to match the desired characters correctly.

$string = "Hello, world!";

// Match the literal exclamation mark without being affected by PHP's escape sequences
$pattern = '/!/';

if (preg_match($pattern, $string)) {
    echo "Exclamation mark found!";
} else {
    echo "Exclamation mark not found.";
}