PHP $_POST undefined variable (using JQuery AJAX) - php

Question

I submit my form with JQuery Ajax in php as this :
$("#addForm").submit( function() {
//var valid = jQuery("#addForm").validationEngine('validate');
var valid = true;
if(valid==true) {
// recuperer toutes les informations
var name = $("#name").val();
var type = $('select#type option:selected').val();
var region = $('select#region option:selected').val();
var level = $('select#level option:selected').val();
var nbPers = $("#number_person").val();
var tempsPre = $("#time_pre").val();
var tempsC = $("#time_c").val();
var ings = $("#ing_hide").val();
var etapes = $("#preparation").val();
$.ajax({
type: "POST",
url: "php/add.php",
data: "name="+name+"&type="+type+"&region="+region+"&level="+level+"&nbPers="+nbPers+"&tempsPre="+tempsPre+"&tempsCui="+tempsC+"&ings="+ings+"&etapes="+etapes,
error : function(request, error) {
alert("Erreur : responseText: "+request.responseText);
},
success: function(msg){ // si l'appel a bien fonctionné
alert('ok');
}
});
return false;
} else {
alert('error');
return false;
}
});
when I debug using firebug, all my variables were correct
but in php files , the var_dump show : undefined for var_dump($_POST['name']); and correct value for var_dump($_POST['ings']);
Note: I dont use isset because I'm only testing that the variable contains value in first
Why I've undefined ?
My HTML form :
<div class="row field_text">
<label class="label_title">Nom :</label>
<input type="text" class="inputtext" name="name" id="name"/>
</div>
<div class="row field_select">
<label class="label_title">Type :</label>
<select class="select_styled" name="type" id="type">
<option value="1">E</option>
<option value="2">P</option>
<option value="3">D</option>
<option value="4">B</option>
</select>
</div>
<div class="row">
<label>Region</label>
<select class="select_styled" name="region" id="region">
<option value="1">Ma</option>
<option value="2">Eu</option>
<option value="3">Af</option>
<option value="4">Mo</option>
<option value="5">As</option>
</select>
</div>
<div class="row field_select">
<label class="label_title">Difficulté :</label>
<select class="select_styled" name="level" id="level">
<option value="1">F</option>
<option value="2">M</option>
<option value="3">D</option>
</select>
</div>
<div class="row field_text">
<label class="label_title">Nombre Personne :</label>
<input type="text" class="inputtext" name="number_person" id="number_person"/>
</div>
<div class="row field_text">
<label class="label_title">Temps pré :</label>
<input type="text" class="inputtext" name="time_pre" id="time_pre"/>
</div>
<div class="row field_text">
<label class="label_title">Temps cui :</label>
<input type="text" class="inputtext" name="time_cook" id="time_cook"/>
</div>
<div class="clear"></div>
<div class="ings_div">
<div class="row field_select">
<label for="ingredient" class="label_title">Ingrédient :</label>
<select id="ingredient" name="basic-combo" size="1" class="select_styled">
<?php include('php\liste-ingredients.php');?>
</select>
</div>
<div class="row field_text">
<label class="label_title">Quantité :</label>
<input id="quantite" type="text" class="inputtext" name="recette_quantite"/>
</div>
<div class="row field_select">
<label class="label_title">Unité :</label>
<select id="unite" class="select_styled" name="unite">
<?php include('php/liste-unites.php'); ?>
</select>
</div>
<div class="row rowSubmit">
<input id="btn_add_ing" type="submit" value="+">
</div>
<div class="rowIng">
<label class="label_title">Liste Ingrédients :</label>
<textarea id="recette_ingredient" class="textareaField required" name="recette_ingredient" cols="5" rows="4"></textarea>
</div>
<div class="rowIngHide">
<label class="label_title">Liste Ingrédients :</label>
<textarea id="recette_ingredient_hide" class="textareaField required" name="recette_ingredient_hide" cols="5" rows="4"></textarea>
</div>
<div class="clear"></div>
</div>
<div class="clear"></div>
<div class="preparation_div">
<div class="">
<label class="label_title">Préparation :</label>
<textarea class="textareaField required" name="preparation" id="preparation" cols="8" rows="4"></textarea>
</div>
</div>
<div class="clear"></div>
<div class="row rowSubmit">
<span class="btn btn_search"><input type="submit" value="Ajouter"></span>
</div>
</form>