using $_POST in if statement - php

Question

Suppose I have the html code below:
<FORM name="myForm" action="confirmsold.php" method="post" onsubmit="return validateFormCash()">
<table border=0 width="300" cellspacing=1 cellpadding=3 bgcolor="#353535" align="center">
<tr>
<br>
<tr>
<td bgcolor="#ffffff" colspan=2 width="30%"><b> Input Payment Details (CASH)<b></td>
</td>
</tr>
<tr>
<td bgcolor="#ffffff">Payment Type:</td>
<td bgcolor="#ffffff"><input type="text" name="paytype" value="Cash" disabled></td>
</tr>
<tr>
<td bgcolor="#ffffff">Date Sold:</td>
<td bgcolor="#ffffff"><input type="date" name="date" value="<?php echo date('Y-m-d'); ?>"></td>
</tr>
<tr>
<td bgcolor="#ffffff">Cash Amount:</td>
<td bgcolor="#ffffff"><INPUT type="TEXT" name="cashamount" size="10" maxlength="9" onkeypress="if ( isNaN( String.fromCharCode(event.keyCode) )) return false;"></INPUT></td>
</tr>
<td bgcolor="#ffffff" colspan=2 align="center">
<INPUT type="submit" name="submit" value="Submit">
</td>
</tr></form>
As you can see, it has a default value of "CASH". Now this will be submitted to a php page with an if statement:
if ($_SERVER['REQUEST_METHOD'] == 'POST' && $_POST['paytype'] == 'Cash') {
This is the Javascript im using for the form:
function validateFormCash() {
var x = document.forms["myForm"]["cashamount"].value;
if (x == null || x == "") {
alert("Please input Cash Amount");
return false;
}
}
But the page will return an error saying undefined paytype, what am I missing here? Anyone please help.
Thank you

Answer 1

Write this in if conditional:
if ($_SERVER['REQUEST_METHOD'] == 'POST' && $_POST['submit']) {
To be able to catch this $_POST, you have to put input field in form. For example:
<form action="" method="POST">
<!-- some HTML here, including <table> tag -->
<tr>
<td bgcolor="#ffffff">Payment Type:</td>
<td bgcolor="#ffffff"><input type="text" name="paytype" value="Cash"></td>
</tr><tr>
<td bgcolor="#ffffff" colspan=2 align="center">
<INPUT type="submit" name="submit" value="Submit">
</td>
</tr>
<!-- Some more HTML here, including </table> end tag -->
</form>