How can PHP developers ensure that a specific value, like the number "4," is only found as a standalone entity within a comma-separated string?

To ensure that a specific value, like the number "4," is only found as a standalone entity within a comma-separated string, PHP developers can use regular expressions to match the exact value surrounded by commas. By using the regex pattern "\b4\b", developers can match the number "4" only when it is a standalone entity within the string.

$string = "1,2,3,4,5";
$pattern = "/\b4\b/";
if (preg_match($pattern, $string)) {
    echo "Number 4 found as a standalone entity in the string.";
} else {
    echo "Number 4 not found as a standalone entity in the string.";
}