php isset($_post[]) and javascript form.submit

Question

for some reason isset($_post) doesn't work when i use js form.submit() how i can resolve that without changing type of input from button to submit and just with using vanilla javascript because i need both of them.

code html:

<form name="user_verification" action="action.php" method="POST">
 Name: <input type="text" name="name"><br>
E-mail: <input type="text" name="email"><br>
<input type="button" onclick="myFunction(this)" name="button" value="submit">
</form>

and here is the php script in action.php file

if($_SERVER['REQUEST_METHOD']=="POST")
{
if(isset($_POST['button'])) 
{
echo 'yes';
}else{
echo 'no';
}
}

and here is the javascript in action.js file

function myFunction(button)
{
//some code
const form=button.parentNode;
form.submit();}

Answer 1

Actually the problem didn't raise from the PHP. Buttons' value is sent when the form is directly submitted by them (In this case, it seems impossible).

Suggestion 1: use another field to check form submission.

if($_SERVER['REQUEST_METHOD'] == 'POST') {
    if(isset($_POST['email'])) {
        echo 'yes';
    } else {
        echo 'no';
    }
}

Suggestion 2: add hidden input in the HTML.

<form name="user_verification" action="test.php" method="POST">
    Name: <input type="text" name="name"><br>
    E-mail: <input type="text" name="email"><br>
    <input type="hidden" name="button" value="submit">
    <input type="button" onclick="myFunction(this)">
</form>

Suggestion 3: change button type to hidden before submitting.

function myFunction(button) {
    // some code
    button.setAttribute('type', 'hidden');
    const form=button.parentNode;
    form.submit();
    button.setAttribute('type', 'button');
}