在javascript中isset（$ _ POST ['name']）的等价物是什么？

Question

I have two forms (consisting of checkboxes) on two different PHP pages. I want to use the values submitted from the first form to disable checkboxes in the second form.

page1.php:

<form method="POST" action="page2.php">
<input type="checkbox" id="1">
<input type="checkbox" id="2">
<input type="checkbox" id="3">
<input type="checkbox" id="4">
<input type="checkbox" id="5">
<input type="checkbox" id="6">
<input type="submit">
</form>

page2.php:

<form method="POST" action="action.php">
<input type="checkbox" id="1">
<input type="checkbox" id="2">
<input type="checkbox" id="3">
<input type="checkbox" id="4">
<input type="checkbox" id="5">
<input type="checkbox" id="6">
<input type="submit">
</form>

<script>
if(!isset($_POST['2'])){
document.getElementById("4").disabled = true;
}
</script>

What should I use instead of this?

if(!isset($_POST['2']))

I can't use jQuery due to professor limitations.

Answer 1

First don't forget that you need name attributes on your checkboxes for PHP. Second, although your ids are valid in HTML5, I'd change them to start with a letter to make them HTML4 compatible.

I print the POST variable using php and assign it to post in javascript. Then I check if the checkbox exists in the post variable.

page1.php:

<form method="POST" action="page2.php">
<input type="checkbox" id="1" name="box1">
<input type="checkbox" id="2" name="box2">
<input type="checkbox" id="3" name="box3">
<input type="checkbox" id="4" name="box4">
<input type="checkbox" id="5" name="box5">
<input type="checkbox" id="6" name="box6">
<input type="submit">
</form>

page2.php:

<form method="POST" action="action.php">
<input type="checkbox" id="1">
<input type="checkbox" id="2">
<input type="checkbox" id="3">
<input type="checkbox" id="4">
<input type="checkbox" id="5">
<input type="checkbox" id="6">
<input type="submit">
</form>

<script>
var post = <?php echo json_encode($_POST) ?>;
if (!post.box2) document.getElementById("4").disabled = true;

</script>