我想在我点击提交按钮时更改定义功能的值

Question

 code.. this is a aa.php file
 <?php
 include("text.php"); 
 ?>
 <form method="post" action="text.php">
 Add product helper text: <input type="text" name="add_product"size="30" value="<?php echo $a;?>" >
<input type="submit" name="submit" value="Submit">
</form> this is a aa.php file... as i click the submit button i need to change the value in define function
<?php
define("product","function exists Return TRUE if the given function has been defined",TRUE);
$a = constant("product");
?>

这是text.php文件..当我编辑add_product字段的值时，更改将反映在text.php文件的define函数中...就像我在textfield中编辑＆＃34;函数存在返回TRUE＆ ＃34;那么函数将成为定义（＆＃34;产品＆＃34;，＆＃34;函数存在返回TRUE＆＃34;，TRUE）;