PHP: Regex Validation

validate.php

<?php
	// ref: http://komunitasweb.com/2009/03/10-practical-php-regular-expression-recipes/
	// Validate Email
	if (filter_var('[email protected]', FILTER_VALIDATE_EMAIL)) {
	    echo "Your email is ok.";
	} else {
	    echo "Wrong email address format.";
	}

	//Validate Username
	$username = "user_name12";
	if (preg_match('/^[a-z\d_]{5,20}$/i', $username)) {
	    echo "Your username is ok.";
	} else {
	    echo "Wrong username format.";
	}

	//Validate US Phone # 
	$phone = "(021)423-2323";
	if (preg_match('/\(?\d{3}\)?[-\s.]?\d{3}[-\s.]\d{4}/x', $phone)) {
	    echo "Your phone number is ok.";
	} else {
	    echo "Wrong phone number.";
	}

	//Validate IP addresses
	$IP = "198.168.1.78";
	if (preg_match('/^(([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]).){3}([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$/',$IP)) {
	    echo "Your IP address is ok.";
	} else {
	    echo "Wrong IP address.";
	}

	// Validate Us Postal Codes
	$zipcode = "12345-5434";
	if (preg_match("/^([0-9]{5})(-[0-9]{4})?$/i",$zipcode)) {
	    echo "Your Zip code is ok.";
	} else {
	    echo "Wrong Zip code.";
	}

	// Validate SSN
	$ssn = "333-23-2329";
	if (preg_match('/^[\d]{3}-[\d]{2}-[\d]{4}$/',$ssn)) {
	    echo "Your SSN is ok.";
	} else {
	    echo "Wrong SSN.";
	}

	// CC Validation
	$cc = "378282246310005";
	if (preg_match('/^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6011[0-9]{12}|3(?:0[0-5]|[68][0-9])[0-9]{11}|3[47][0-9]{13})$/', $cc)) {
	    echo "Your credit card number is ok.";
	} else {
	    echo "Wrong credit card number.";
	}

	// URL validation
	$url = "http://komunitasweb.com/";
	if (preg_match('/^(http|https|ftp):\/\/([A-Z0-9][A-Z0-9_-]*(?:\.[A-Z0-9][A-Z0-9_-]*)+):?(\d+)?\/?/i', $url)) {
	    echo "Your url is ok.";
	} else {
	    echo "Wrong url.";
	}

	// Return Domain from exact url
	$url = "http://komunitasweb.com/index.html";
	preg_match('@^(?:http://)?([^/]+)@i', $url, $matches);
	$host = $matches[1];
	echo $host;

	// Highlight word
	text = "Sample sentence from KomunitasWeb, regex has become popular in web programming. Now we learn regex. According to wikipedia, Regular expressions (abbreviated as regex or regexp, with plural forms regexes, regexps, or regexen) are written in a formal language that can be interpreted by a regular expression processor";
	$text = preg_replace("/\b(regex)\b/i", '<span style="background:#5fc9f6">\1</span>', $text);
 	echo $text;