Creating a basic bad word filter in PHP -

This tutorial will show you how to create a basic bad word filter in PHP.
<?php
if(isset($_POST['submit']))
{
$data = $_POST['data'];
$data2 = $_POST['data2'];
$data3 = $_POST['data3'];
$name=array($data,$data2,$data3);
foreach ($name as $name)
{
if (preg_match("/%/",$name)) {
echo "<center>Invalid Characters: % <a href=\"javascript:history.go(-1)\">Go Back</a></center>";  
Die();
}
if (preg_match("/</",$name)) {
echo "<center>Invalid Characters: < <a href=\"javascript:history.go(-1)\">Go Back</a></center>";  
Die();
}
if (preg_match("/xxx/",$name)) {
echo "<center>Invalid Characters: xxx <a href=\"javascript:history.go(-1)\">Go Back</a></center>";  
Die();
}
}
echo $data;
echo"<br />";
echo $data2;
echo"<br />";
echo $data3;
echo"<br />";
}else{
?>
<form action="index.php" method="post">
<input type="text"  name="data"><br>
<input type="text"  name="data2"><br>
<input type="text"  name="data3"><br>
<input type="submit" name="submit" value="demo"><br>
</form>
<?php
}
?>