Question

HTML:

<form name="myform" action="process.php" method="POST">
    <input type="hidden" name="check_submit" value="1" />
    <!-- ........ -->
</form>

PHP:

if (array_key_exists('check_submit', $_POST)) {....}

Why can array_key_exists('check_submit', $_POST) check whether the form was submitted?

I’ve seen isset($_POST['...']) used before, but not this.

if i don’t do this array_key_exists(‘check_submit’, $_POST) decision., what may happen.

Answer 1

check_submit is a field in your form, so when you submit the form, that field is available in the POST data.

PHP places incoming POST-method form data into the $_POST superglobal array, and your code determines whether the check_submit field can be found in that array.

Indeed, it’s quite similar to isset($_POST['check_submit']), in that it checks whether such an element exists in $_POST. It’s just taking a slightly different approach.

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If you did not submit the form, then of course there is no form data.