<!DOCTYPE HTML>
<html>
<head>
<style>
.error_message {color: #FF0000;}
</style></head>
<body>
<?php
$err_msg = "";
$url = "";
if ($_SERVER["REQUEST_METHOD"] == "POST")
{
if (empty($_POST["url"]))
{
$url = "";
}
else
{
$url = clean_input($_POST["url"]);
// check if URL is valid
if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i", $url))
{
$err_msg = "Invalid URL";
}
else
$err_msg = "";
}
}
function clean_input($data)
{
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?><h3>Form Validation With PHP</h3>
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
URL: <input type="text" name="url">
<span class="error_message">* <?php echo $err_msg;?></span>
<br /><br />
<input type="submit" name="submit" value="Submit">
</form>
<?php
echo "URL = " . $url;
?>
</body>
</html>
