Request form and POST in a single go? - php

Question

Please excuse the poor title.
I am a total beginner and don't know the right terms to make it better.
I am trying to POST form data using PHP.
My problem is that before i POST the form data i need to get a value from the form, that is changing each time i request the page.
Please notice the second input, the value is auto generated and is a random number each time i request the form.
Here is my form.php:
<?php
if(!isset($_REQUEST['submit_btn'])){
echo '
<form action="'.$_SERVER['PHP_SELF'].'" method="POST">
<input type="text" name="user_name" id="user_name">
<input type="hidden" name="a_random_password" value="'.(rand(10,100)).'">
<input type="submit" value="submit" name="submit_btn">
</form>';
}
if(isset($_REQUEST['submit_btn']))
{
$user_name= $_POST["user_name"];
$a_random_password = $_POST["a_random_password"];
echo "Your User Name is:". $user_name;
echo "<br> and your Password is : $a_random_password;
}
?>
And my post.php
<?php
$url = "http://test.com/form.php";
$data = array(
'user_name' => 'John',
'a_random_password' => 'xxx',
'submit' => 'submit'
);
$options = array(
'http' => array(
'header' => "Content-type: application/x-www-form-urlencoded\r\n",
'method' => 'POST',
'content' => http_build_query($data)
)
);
$context = stream_context_create($options);
$result = file_get_contents($url, false, $context);
if ($result === FALSE) { echo "Error"; }
var_dump($result);
?>
So how do i get the a_random_password value and submit it along with the form in a single request, else the password wont fit with the user name.

Answer 1

Sup, what you wanna do is impossible using PHP in that way, cause the only job PHP has is to render your content on server side. To listen to the client side you'll need to use javascript.
let randomPassword = document.getElementById('a_randow_password')
let name = document.getElementById('name')
let password = document.getElementById('password')
name.onkeyup = function(){
password.value = randomPassword.value + name.value
}
<input type="text" id="name" name="user_name" placeholder="name"><br />
<input type="hidden" name="a_random_password" id="a_randow_password" value="xxx">
<input type="text" id="password" placeholder="password"><br />

Answer 2

Not sure exactly what you trying to achieve, but if You want to interrupt a request (and modify|use it) from HTML to PHP, You need AJAX request (JavaScript).