PHP simple human verfication

Copy this below code

<?php
if(isset($_POST['submit'])) {
$code1=$_POST['code1'];
$code=$_POST['code'];
if($code1!="$code"){
$msg="Invalide code"; }
else
{
$msg="Your code is correct";
}
}
?>

<form name="form" method="post">
<p>Type Below this code
<?php $Random_code=rand(5000,1000); echo$Random_code; ?>
</p>
<p>Enter the random code<br />
<input type="text" name="code1" title="random code" />
<input type="hidden" name="code" value="<?php echo $Random_code; ?>" />
</p>
<p>
<input type="submit" value="check" title="code check" name="submit"/>
</p>
</form>
<p>
<?php if(isset($_POST['submit']))
{ echo $msg; } ?>
</p>