example_validattion.php

<?php
 
    if (isset($_POST['Submit'])) {
 
        if ($_POST['name'] != "") {
            $_POST['name'] = filter_var($_POST['name'], FILTER_SANITIZE_STRING);
            if ($_POST['name'] == "") {
                $errors .= 'Please enter a valid name.<br/><br/>';
            }
        } else {
            $errors .= 'Please enter your name.<br/>';
        }
 
        if ($_POST['email'] != "") {
            $email = filter_var($_POST['email'], FILTER_SANITIZE_EMAIL);
            if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
                $errors .= "$email is <strong>NOT</strong> a valid email address.<br/><br/>";
            }
        } else {
            $errors .= 'Please enter your email address.<br/>';
        }
 
        if ($_POST['homepage'] != "") {
            $homepage = filter_var($_POST['homepage'], FILTER_SANITIZE_URL);
            if (!filter_var($homepage, FILTER_VALIDATE_URL)) {
                $errors .= "$homepage is <strong>NOT</strong> a valid URL.<br/><br/>";
            }
        } else {
            $errors .= 'Please enter your home page.<br/>';
        }
 
        if ($_POST['message'] != "") {
            $_POST['message'] = filter_var($_POST['message'], FILTER_SANITIZE_STRING);
            if ($_POST['message'] == "") {
                $errors .= 'Please enter a message to send.<br/>';
            }
        } else {
            $errors .= 'Please enter a message to send.<br/>';
        }
 
        if (!$errors) {
            $mail_to = 'me@somewhere.com';
            $subject = 'New Mail from Form Submission';
            $message  = 'From: ' . $_POST['name'] . "\n";
            $message .= 'Email: ' . $_POST['email'] . "\n";
            $message .= 'Homepage: ' . $_POST['homepage'] . "\n";
            $message .= "Message:\n" . $_POST['message'] . "\n\n";
            mail($to, $subject, $message);
 
            echo "Thank you for your email!<br/><br/>";
        } else {
            echo '<div style="color: red">' . $errors . '<br/></div>';
        }
    }
?>
 
<form name="form1" method="post" action="form-email.php">
Name: <br/>
<input type="text" name="name" value="<?php echo $_POST['name']; ?>" size="50" /><br/><br/>
Email Address: <br/>
<input type="text" name="email" value="<?php echo $_POST['email']; ?>" size="50"/> <br/><br/>
Home Page: <br/>
<input type="text" name="homepage" value="<?php echo $_POST['homepage']; ?>" size="50" /> <br/><br/>
Message: <br/>
<textarea name="message" rows="5" cols="50"><?php echo $_POST['message']; ?></textarea>
<br/>
<input type="submit" name="Submit" />
</form>