Find an html element by id and replace its contents with php - php

Question

I have an html with submit button.
Submit sends you to php.
php code has this:
header("location:./setupOk.html");
$html = file_get_html('setupOk.html');
$ret = $html->find('div[id=valueOk]');
echo $ret[0]->innertext = "foo";
and this is some of my html setupOk.html code:
<form action="http://54.186.92.18/Pixel-Matrix/keys.php" method="post">
<div class="logo">
<link rel="stylesheet" type="text/css" href="styles.css">
<label id="logo"</label>
<!--<label for="name">Type:</label>-->
</div>
<div class="right">
<h1>Enter License Information</h1>
<div id="valueOk">
<input type="text" id="valOk" name="Key" readonly="readonly" />
</div>
</div>
<div class="button">
<button id="validateB" type="submit">Validate Now ></button>
</div>
</form>
After executing button on first html, it goes to php and reloads my html website with setupOk but no text is innered to anywhere. Any solution?
EDIT:
my goal is to have a general html (with label and images) then from php, put text to that html and automatically load this html on user's browser
EDIT2:
MY FIRST HTML ISN'T THE SAME THAN 2ND HTML. FIRST ONE SENDS POST PETITION TO PHP THEN DEPENDING ON THE INFO SENT TO PHP, PHP WILL FILL TEXT TO THE 2ND HTML AND LOAD THIS LAST HTML ON USER'S BROWSER

Answer 1

Avoiding DOMParser and loading/redirecting to HTML page -- you can do it more simple way like (it has to be a PHP file):
<?php
$innerText = "";
if (!empty($_POST['Key'])) {
$innerText = "foo";
}
?>
<div class="logo">
<link rel="stylesheet" type="text/css" href="styles.css">
<label id="logo"</label>
<!--<label for="name">Type:</label>-->
</div>
<div class="right">
<h1>Enter License Information</h1>
<div id="valueOk">
<input type="text" id="valOk" name="Key" readonly="readonly" value="<?php echo $innerText;?>"/>
</div>
</div>
<div class="button">
<button id="validateB" type="submit">Validate Now ></button>
</div>
If you think this is not what you want - please elaborate your need a bit.
UPDATE
setupOk.php
<form action="http://54.186.92.18/Pixel-Matrix/keys.php" method="post">
<div class="logo">
<link rel="stylesheet" type="text/css" href="styles.css">
<label id="logo"</label>
<!--<label for="name">Type:</label>-->
</div>
<div class="right">
<h1>Enter License Information</h1>
<div id="valueOk">
<input type="text" id="valOk" name="Key" readonly="readonly" />
</div>
</div>
<div class="button">
<button id="validateB" type="submit">Validate Now ></button>
</div>
</form>
keys.php [where you are submitting the form]
require_once('simple_html_dom.php');
$processedResult = "";
if (!empty($_POST['Key'])) {
$processedResult = "foo";
}
$html = file_get_html('setupOk.php');
$html->find('input[id=valOk]', 0)->value = $processedResult;
echo $html;
I have tested it and it's working.