What are the potential differences in results when using different regular expression patterns in PHP for string validation?

When using different regular expression patterns in PHP for string validation, the potential differences in results can include variations in what is considered a valid or invalid input. Different patterns may have different rules for what constitutes a valid string, such as the presence of certain characters or the length of the string. It's important to carefully choose the appropriate regular expression pattern that aligns with the specific validation requirements for the input data.

// Example of using a specific regular expression pattern for email validation
$email = "example@example.com";

if (preg_match("/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/", $email)) {
    echo "Valid email address";
} else {
    echo "Invalid email address";
}