What to use instead of if(isset($_POST['submit'])) for this.form.submit()?

Question

I want to run a particular block of PHP if the user submits a form. It works if I use a submit button with name="submit" and:

<?php
if(isset($_POST['submit'])) {
code to run
}
?>

I don't know anything about javascript, and I want the code to run if the user changes a dropdown menu. If I make the first line of the dropdown

<select name="dropdownname" onchange="this.form.submit()">

the form appears (I haven't tested it) to submit if the user changes the dropdown choice. However, if I do this, the if(isset($_POST['submit'])) PHP code doesn't run. Is there a PHP if statement I can write that will respond to the form being submitted even though it's being submitted by a change in the dropdown and not a submit button?

Answer 1

您可能需要直接检查：

if(isset($_POST['dropdownname']))

Answer 2

Even you can use something like:

 if(count($_POST)){
 // form validation
 } else {
 //...
 }

Answer 3

你应该总是检查$ _SERVER ['REQUEST_METHOD']而不是特定的字段名称

Answer 4

如果此下拉列表用于显示某些数据，而不是写入数据库，则应使用GET方法。

Answer 5

<?php

if(!empty($_POST))
{
    code to run
}

?>