addClient.php

<?php 
require_once 'inc/header.php';
require_once 'inc/config.php';
require_once 'inc/function.php';

// Get all Wilaya

/****************************************************/
 $sqlw = "SELECT * FROM wilaya";
 $resw = mysqli_query($connect,$sqlw);


/***************************************************/





 ?>


<style>
	.alert{display: none}
</style>

<div class="container mt-5">
  <div class="row">
    <div class="col">


		<div class="alert alert-success" role="alert">
		  A simple success alert—check it out!
		</div>
		<div class="alert alert-danger" role="alert">
		  A simple danger alert—check it out!
		</div>



		<form id="forms">
		  <div class="form-row">
		    <div class="form-group col-md-6">
		 
		      <input type="text" name="nom" class="form-control" id="nom" placeholder="Nom">
		    </div>
		    <div class="form-group col-md-6">
		      <input type="text" name="prenom" class="form-control" id="prenom" placeholder="Prénom">
		    </div>
		  </div>
		  <div class="form-group">
		    <input type="email" name="email" class="form-control" id="email" placeholder="Email">
		  </div>
		  <div class="form-group">
		    <input type="tel" name="tel" class="form-control" id="tel" placeholder="Tel Number">
		  </div>

		   <div class="form-group">
		   <select name="wilaya_id" >

     	  	<?php 
     	  	while ($data = mysqli_fetch_array($resw)):

     	  	 ?>
		   	<option value="<?=$data['id'] ?>"><?=$data['nom'] ?></option>
			    <?php endwhile; ?>
		   </select>
		  </div>

		  <input type="hidden" name="add" value="ok">
		 
		  <button type="submit" id="btn" class="btn btn-primary btn-lg">Add Client</button>
		</form>



    </div>
    
  </div>
</div>

 <?php 
require_once 'inc/footer.php';

 ?>

app.js

$(document).ready(function() {
	
	$("body").on('click', '#btn', function(event) {
		event.preventDefault();
		//alert('test')
/*		let nom = $('#nom').val()
		let prenom = $('#prenom').val()
		let email = $('#email').val()
		let tel = $('#tel').val()
		let w = $('#wilaya_id').val()*/

		var donnee = $("#forms").serializeArray()
		//console.log(data);
// New
/*		$.ajax({
			url: 'addAjax.php',
			type: 'POST',
			
			data: donnee,
		})
		.done(function(req) {
			if (req==1) {
				$('.alert-success').show(3000).delay(5000).hide(3000,function () {
					window.location.href ='listClient.php'
				})


			}else{
				$('.alert-danger').show(3000).hide(3000)
			}
		})
		.fail(function() {
			console.log("error");
		})
		*/

		// Old

		$.ajax({
			url:'addAjax.php',
			type: 'POST',
			data: donnee,
			beforeSend:function () {
				   $("#forms").trigger("reset");
			   $('#btn').text('Loading ...').removeClass('btn-primary').addClass('btn-danger')
			},
			success:function(req){
				  $('#btn').text('OKKKK').removeClass('btn-danger').addClass('btn-primary')
				if (req==1) {
								$('.alert-success').show(3000).delay(5000).hide(3000,function () {
									window.location.href ='listClient.php'
								})


							}else{
								$('.alert-danger').show(3000).hide(3000)
							}
			}
		})
		
	});
});

gistfile1.txt

<?php 

require_once 'inc/config.php';
require_once 'inc/function.php';

// Get all Wilaya

/****************************************************/
 $sqlw = "SELECT * FROM wilaya";
 $resw = mysqli_query($connect,$sqlw);


/***************************************************/

$data['nom'] = (isset($_POST['nom']))?$_POST['nom']:null;
$data['prenom']  = (isset($_POST['prenom']))?$_POST['prenom']:null;
$data['tel']  = (isset($_POST['tel']))?$_POST['tel']:null;
$data['email']  = (isset($_POST['email']))?$_POST['email']:null;
$data['wilaya']  = (isset($_POST['wilaya_id']))?$_POST['wilaya_id']:null;
$add = (isset($_POST['add']))?$_POST['add']:null;
if ($add=='ok') {
	  if (addClient($data)==1) {
	  	echo 1;
	  }else echo 0;


}



 ?>