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PHP Web Based Regex Functions - Email, Username, Domain Validation

Learn how to validate email addresses, usernames, and domains using regex functions in web programming.

<?php

if (filter_var('test+email@fexample.com', FILTER_VALIDATE_EMAIL)) {
    echo "Your email is ok.";
} else {
    echo "Wrong email address format.";
}

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

$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.";
}

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

$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;

?>

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