php code run unly on lick code example

Example 1: php unset

// Destroy a variable
<?php
unset ($var1, $var2.... )
?>

Example 2: php disable buutton

<input type="button" value="Add to Cart" <?php if ($prod_qty == '0'){ ?> disabled <?php   } ?> onclick="addtocart(<?php echo $row["prod_id"]?>)" />