$_POST [] array is empty after submission - php

Question

So $_POST['acc'], and $_POST['psw'] can't get data from the form for some reason, they are empty all the time.
html:
<div id="signUp_UI">
<form id="su_form" action="<?php echo url_for('/sign_up.php')?>" method="post" enctype="multipart/form-data">
YYQ<br><br>
Account Name<br>
<input type="text" placeholder="Account Name" id="an" name="acc">
<br><br>
Passward<br>
<input type="password" placeholder="Password" id="password" name="psw">
<br><br>
<input type="button" name="goback" value="Go Back" id="gb_button">
<input type="submit" value="Sign Up" id="su_button2">
</form>
</div>
php:
$an = isset($_POST['acc']) ? $_POST['acc'] : '';
$psw = isset($_POST['psw']) ? $_POST['psw'] : '';
$sql = "INSERT INTO log_in (account, password) VALUES ('". $an . "'," . "'" . $psw . "')";
$result = mysqli_query($db, $sql);
if($result){
$new_id = mysqli_insert_id($db);
redirect_to(url_for('/home.php?id=') . $new_id);
}
else{
echo mysqli_error($db);
db_disconnect($db);
exit();
}
Update:
So if I change php code to:
if(is_post_request()){
$an = isset($_POST['acc']) ? $_POST['acc'] : '';
$psw = isset($_POST['psw']) ? $_POST['psw'] : '';
$sql = "INSERT INTO log_in (account, password) VALUES ('". h($an) . "'," . "'" . h($psw) . "');";
$result = mysqli_query($db, $sql);
if($result){
echo '$an = ' . $an .'<br>';
echo '$psw = ' . $psw;
}
else{
echo mysqli_error($db);
db_disconnect($db);
exit();
}
then I got the result:
$an =
$psw =
UPDATE:
So I tried to detect isset($_POST['submit']) in php file, the result is $_POST['submit'] does not exist.
So it's like after I've submit the form, it isn't been sent to the php file for some reason.
UPDATE 3.0:
So if i change method to get, everything works find! I don't know why is that.
html:
<div id="signUp_UI">
<form id="su_form" action="<?php echo url_for('/sign_up.php'); ?>" method="get">
YYQ GameStation<br><br>
Account Name<br>
<input type="text" placeholder="Account Name" id="an" name="account">
<br><br>
Password<br>
<input type="password" placeholder="Password" id="password" name="password">
<br><br>
<input type="button" name="goback" value="Go Back" id="gb_button">
<input type="submit" name = "submit" value="Sign Up" id="su_button2">
</form>
</div>
php:
if(isset($_GET['submit']) && !empty($_GET['submit'])){
$an = isset($_GET['account'])?$_GET['account']:'';
$psw = isset($_GET['password'])?$_GET['password']:'';
$sql = "INSERT INTO log_in (account, password) VALUES ('". h($an) . "'," . "'" . h($psw) . "');";
$result = mysqli_query($db, $sql);
if($result){
redirect_to(url_for('/home.php'));
}
else{
echo mysqli_error($db);
db_disconnect($db);
exit();
}

Answer 1

Alright, according to sources I've found, it seems that there is something wrong with phpstrom build-in server. POST method somehow just doesn't work.
Reference ~ https://intellij-support.jetbrains.com/hc/en-us/community/posts/206999125-PhPStorm-10-does-not-allow-POST-method

Answer 2

Why you need to do this?
<form id="su_form" action="<?php echo url_for('/sign_up.php')?>" method="post" enctype="multipart/form-data">
Can you try to replace this
from:
action="<?php echo url_for('/sign_up.php')?>"
to:
action="sign_up.php"