Getting a value from url and using it in sql query - php

Question

I'm working on a complex project for a car dealership where I have to create database search based on multiple criteria. The cars in the database are divided into 3 types - let's call them A, B and C. Let's say that the value of A=1, B=2, C=3. The url would look something like index.php?type_id=1 . The working search code so far is as follows.
In index.php :
<script type="text/javascript">
$(document).ready(function(){
$('#car').on('change',function(){
var carID = $(this).val();
if(carID){
$.ajax({
type:'POST',
url:'ajaxData.php',
data:'marque_id='+carID,
success:function(html){
$('#model').removeAttr("disabled");
$('#model').html(html);
}
});
}else{
$('#model').attr("disabled");
$('#energy').attr("disabled");
}
});
});
</script>
$type_id = $_GET['type_id];
$query = $db->query("SELECT DISTINCT marque_name,a.marque_id FROM vehicule_marque as a INNER JOIN vehicule as b WHERE b.type_id = '$type_id' AND a.marque_id = b.marque_id order by marque_name");
$rowCount = $query->num_rows;
<div>Select car</div>
<select name="car" id="car" required >
<option value="">Select Car</option>
<?php
if($rowCount > 0){
while($row = $query->fetch_assoc()){
echo '<option value="'.$row['marque_id'].'">'.$row['marque_name'].'</option>';
}
}else{
echo '<option value="">Car not available</option>';
}
?>
</select>
<div>Select car model</div>
<select name="model" id="model" disabled>
<option value=""><!--Select car first--></option>
</select>
In ajaxData.php :
if(isset($_POST["marque_id"]) && !empty($_POST["marque_id"])) {
//Get all state data
$query = $db->query("SELECT DISTINCT a.modele_id, modele_name, a.marque_id FROM vehicule_modele as a INNER JOIN vehicule as b WHERE a.marque_id = ".$_POST['marque_id']." AND b.type_id = '$type_id' AND b.marque_id = a.marque_id AND b.modele_id = a.modele_id ORDER BY modele_name ");
//Count total number of rows
$rowCount = $query->num_rows;
//Display model list
if($rowCount > 0){
echo '<option value="">Select model</option>';
while($row = $query->fetch_assoc()){
echo '<option value="'.$row['modele_id'].'">'.$row['modele_name'].'</option>';
}
}else{
echo '<option value="">Model not available</option>';
}
}
The problem is with taking the type_id value and using it in ajaxData.php query in order to show the model once the customer selected a car brand. In index.php, I GET the value from the url successfully (I tried echoing it and it worked), but then I can't get it to work in the other query - it keeps on showing only "Model not available" option. I tried putting inside the script the $type_id into a new variable, but this didn't work either. I'm not sure what I'm missing. If I remove the type_id condition, everything works perfectly. If anyone has any idea how to fix this, I would appreciate it.

Answer 1

First of all, you need to understand that request to url index.php?type_id=1 and request to url ajaxData.php are different requests and know nothing about each other.
So, if you try to access $_GET['type_id'] in ajaxData.php you will obviously receive nothing, because $_GET is empty in ajaxData.php. If you send request to ajaxData.php?type_id=42 you will get 42 as $_GET['type_id'].
So, you if you want to use some $_GET or $_POST data in ajaxData.php you must send this data explicitly.
It can be either:
url:'ajaxData.php?type_id=' + yourValue,
// access it with $_GET['type_id']
or
data:'marque_id='+carID+'&type_id='+yourValue,
// access it with $_POST['type_id']