PHP api sends HTTP_response_code(400) no matter what - php

Question

i wrote a Simple PHP crud api and i'm getting HTTP_response_code(400) no matter what i do.
in the api a file named create.php is responsible for inserting new items in the database it checks if the data it receives from ajax isn't empty and then proceeds to creation if it's empty it sends an HTTP_response_code(400).
but, no matter what i do it always sends the HTTP_response_code(400) even though the data is not empty.
i thought the problem was coming from ajax first but after debugging i found out that ajax in facts gets the proper data from the form and sends it.
here is my create.php file
$db = $database->getConnection();
$consumable = new consumable($db);
//get json
$json = file_get_contents("php://input");
// get posted data
$data = json_decode($json);
// make sure data is not empty
if(
!empty($data->reference) &&
!empty($data->price) &&
!empty($data->description) &&
!empty($data->category_id) &&
!empty($data->quantity)
){
// set consumable property values
$consumable->reference = $data->reference;
$consumable->price = $data->price;
$consumable->description = $data->description;
$consumable->category_id = $data->category_id;
$consumable->quantity = $data->quantity;
$consumable->created = date('Y-m-d H:i:s');
// create the consumable
if($consumable->create()){
// set response code - 201 created
http_response_code(201);
// tell the user
echo json_encode(array("message" => "consumable was created."));
}
// if unable to create the consumable, tell the user
else{
// set response code - 503 service unavailable
http_response_code(503);
// tell the user
echo json_encode(array("message" => "Unable to create consumable."));
}
}
else{
// tell the user data is incomplete
// set response code - 400 bad request
//http_response_code(400);
// tell the user
echo json_encode(array("message" => "Unable to create consumable. Data is incomplete."));
echo json_encode($json);
}
and here is my ajax:
$(document).on('submit', '#create-consumable-form', function(){
alert("submit");
// get form data
var form=$(this).serializeObject();
var form_data=JSON.stringify(form);
console.log('a',form);
console.log(form_data);
// submit form data to api
$.ajax({
url: "http://localhost:3000/consumable/create.php",
type : "POST",
contentType : 'application/json',
data : form_data,
success : function(result) {
// consumable was created, go back to consumables list
showconsumables();
},
error: function(xhr, resp, text) {
// show error to console
console.log(xhr, resp, text);
}
});
return false;
});
after filling out the form and submitting instead of adding the entry to the database and sending a 201 OK it shows me the following error:
jquery.js:2 OPTIONS http://localhost:3000/consumable/create.php 400 (Bad Request)
send # jquery.js:2
ajax # jquery.js:2
(anonymous) # create-consumables.js:87
dispatch # jquery.js:2
v.handle # jquery.js:2
index.html:1 Access to XMLHttpRequest at 'http://localhost:3000/consumable/create.php' from origin 'http://localhost:5500' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.
and this is the result of my console.log
a {reference: "BT3000", price: "10", quantity: "5", description: "description", category_id: "3"}
create-consumables.js:85 {"reference":"BT3000","price":"10","quantity":"5","description":"description","category_id":"3"}
the weird thing is when i comment the HTTP_response_code(400) line in my create.php file it works perfectly does anyone have any idea of the cause of this behaviour?

Answer 1

Try to put header() in your create.php file:
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
header("Access-Control-Allow-Methods: POST");
header("Access-Control-Max-Age: 3600");
header("Access-Control-Allow-Headers: Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");

Answer 2

json_decode returns null if it cannot decode it. It seems it does just that. Maybe you need to url_decode and/or stripslashes the contents before you can decode it. As Ahmed is saying, try to output the $data variable and the output of the json_decode and file_get_contents("php://input"); and you will see the mistake soon enough.
Also be aware that !empty(0) and !empty(false) returns true. So if your variable has a value which is 0 or false then it will return 400 in this case as well. This is not the issue in your example, but might become an issue later.

Answer 3

the problem was caused by the fact that the content-type in my headers was application/json and i was using postman for testing and i had left it to default content-type which is text