php dynamic dropdown menu get value - php

Question

i am trying to do a dynamic dropdown menu, i manage to retrieve the first menu value but i can't manage to retrieve the second menu value.
HTML part
<div>
<label for="marca">Marca </label>
<select type="text" id="marca" name="marca" onChange="getModel()">
<option value="">Alege Marca</option>
<?php while($row = mysqli_fetch_assoc($resultMarca)){ ?>
<option value="<?php echo $row["id"] ?>"> <?php echo $row["nume_marca"] ?> </option>
<?php } ?>
</select>
</div>
<div id="model_masina">
<label for="model">Model </label>
<select id="model" nume="model">
<option value="">Alege Model</option>
</select>
</div>
Ajax Part
<script src="//code.jquery.com/jquery-1.12.0.min.js"></script>
<script type ="text/javascript">
function getModel(){
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET","get_model.php?marca="+document.getElementById("marca").value, false);
xmlhttp.send(null);
document.getElementById("model_masina").innerHTML=xmlhttp.responseText;
}
function model_schimba(){
$modelSc = (document.getElementById("model").value);
}
</script>
PHP
?>
<label for="model">Model </label>
<select id="model" nume="model" onchange='model_schimba()'>
<option value="">Alege Model</option>
<?php
while($row = mysqli_fetch_array($res)){ ?>
<option value="<?php echo $row["id"] ?>"> <?php echo $row["name"] ?> </option>
<?php }
?> </select> <?php
}
i mange to take the variable here
$modelSc = (document.getElementById("model").value);
but when i push the submit button i can't reach the variable
$model = $_POST["model"];

Answer 1

"but when i push the submit button i can't reach the variable $model = $_POST["model"];"
nume="model"
PHP syntax is English-based, not in your language.
You need to change it to name="model".
The "name" attribute is the same in any language.
Having use PHP's error reporting, it would have thrown you an undefined index notice.
http://php.net/manual/en/function.error-reporting.php

Answer 2

First, code separation is important for readability.
Second, I think your AJAX return
document.getElementById("model_masina").innerHTML=xmlhttp.responseText;
is mistakenly pointing at a <div> container instead of the <select> list. Should be,
document.getElementById("model").innerHTML=xmlhttp.responseText;
because you are outputting select menu <option>