CORS POST request in ZF2 becomes OPTIONS request instead - php

Is there anyway in Zend Framework 2 to allow CORS on my API?
I have already allowed all origins header("Access-Control-Allow-Origin: *");
Every time I send a POST request with headers the server responds with 405.
On my access log I see the the request is actually OPTIONS


Yes - extend the \Zend\Mvc\Controller\AbstractRestfulController::options method in your controller, if your controller class is extending from it. By default, it returns a 405, which is probably why you see that response.
Headers can be set via \Zend\Http\Headers::addHeaders
Note: "Zend" is currently "Laminas", since Zend Framework has become Laminas.


So to start with your php script should do these checks:
// Allow from any origin
if (isset($_SERVER['HTTP_ORIGIN'])) {
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400'); // cache for 1 day
}
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
header("Access-Control-Allow-Methods: GET, POST, OPTIONS");
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
exit(0);
}
Once you do that CORS will be enabled.

Related

react axios problem when using post method [duplicate]

I have a simple PHP script that I am attempting a cross-domain CORS request:
<?php
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: *");
...
Yet I still get the error:
Request header field X-Requested-With is not allowed by Access-Control-Allow-Headers
Anything I'm missing?

Handling CORS requests properly is a tad more involved. Here is a function that will respond more fully (and properly).
/**
* An example CORS-compliant method. It will allow any GET, POST, or OPTIONS requests from any
* origin.
*
* In a production environment, you probably want to be more restrictive, but this gives you
* the general idea of what is involved. For the nitty-gritty low-down, read:
*
* - https://developer.mozilla.org/en/HTTP_access_control
* - https://fetch.spec.whatwg.org/#http-cors-protocol
*
*/
function cors() {
// Allow from any origin
if (isset($_SERVER['HTTP_ORIGIN'])) {
// Decide if the origin in $_SERVER['HTTP_ORIGIN'] is one
// you want to allow, and if so:
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400'); // cache for 1 day
}
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
// may also be using PUT, PATCH, HEAD etc
header("Access-Control-Allow-Methods: GET, POST, OPTIONS");
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
exit(0);
}
echo "You have CORS!";
}
Security Notes
Check the HTTP_ORIGIN header against a list of approved origins.
If the origin isn't approved, then you should deny the request.
Please read the spec.
TL;DR
When a browser wants to execute a cross-site request it first confirms that this is okay with a "pre-flight" request to the URL. By allowing CORS you are telling the browser that responses from this URL can be shared with other domains.
CORS does not protect your server. CORS attempts to protect your users by telling browsers what the restrictions should be on sharing responses with other domains. Normally this kind of sharing is utterly forbidden, so CORS is a way to poke a hole in the browser's normal security policy. These holes should be as small as possible, so always check the HTTP_ORIGIN against some kind of internal list.
There are some dangers here, especially if the data the URL serves up is normally protected. You are effectively allowing browser content that originated on some other server to read (and possibly manipulate) data on your server.
If you are going to use CORS, please read the protocol carefully (it is quite small) and try to understand what you're doing. A reference URL is given in the code sample for that purpose.
Header security
It has been observed that the HTTP_ORIGIN header is insecure, and that is true. In fact, all HTTP headers are insecure to varying meanings of the term. Unless a header includes a verifiable signature/hmac, or the whole conversation is authenticated via TLS, headers are just "something the browser has told me".
In this case, the browser is saying "an object from domain X wants to get a response from this URL. Is that okay?" The point of CORS is to be able to answer, "yes I'll allow that".

I got the same error, and fixed it with the following PHP in my back-end script:
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST');
header("Access-Control-Allow-Headers: X-Requested-With");

Access-Control-Allow-Headers does not allow * as accepted value, see the Mozilla Documentation here.
Instead of the asterisk, you should send the accepted headers (first X-Requested-With as the error says).
Update:
* is now accepted is Access-Control-Allow-Headers.
According to MDN Web Docs 2021:
The value * only counts as a special wildcard value for requests without credentials (requests without HTTP cookies or HTTP authentication information). In requests with credentials, it is treated as the literal header name * without special semantics. Note that the Authorization header can't be wildcarded and always needs to be listed explicitly.

Many description internet-wide don't mention that specifying Access-Control-Allow-Origin is not enough. Here is a complete example that works for me:
<?php
if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST, GET, DELETE, PUT, PATCH, OPTIONS');
header('Access-Control-Allow-Headers: token, Content-Type');
header('Access-Control-Max-Age: 1728000');
header('Content-Length: 0');
header('Content-Type: text/plain');
die();
}
header('Access-Control-Allow-Origin: *');
header('Content-Type: application/json');
$ret = [
'result' => 'OK',
];
print json_encode($ret);

I've simply managed to get dropzone and other plugin to work with this fix (angularjs + php backend)
header('Access-Control-Allow-Origin: *');
header("Access-Control-Allow-Credentials: true");
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS');
header('Access-Control-Max-Age: 1000');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token , Authorization');
add this in your upload.php or where you would send your request (for example if you have upload.html and you need to attach the files to upload.php, then copy and paste these 4 lines).
Also if you're using CORS plugins/addons in chrome/mozilla be sure to toggle them more than one time,in order for CORS to be enabled

If you want to create a CORS service from PHP, you can use this code as the first step in your file that handles the requests:
// Allow from any origin
if(isset($_SERVER["HTTP_ORIGIN"]))
{
// You can decide if the origin in $_SERVER['HTTP_ORIGIN'] is something you want to allow, or as we do here, just allow all
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
}
else
{
//No HTTP_ORIGIN set, so we allow any. You can disallow if needed here
header("Access-Control-Allow-Origin: *");
}
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 600"); // cache for 10 minutes
if($_SERVER["REQUEST_METHOD"] == "OPTIONS")
{
if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_METHOD"]))
header("Access-Control-Allow-Methods: POST, GET, OPTIONS, DELETE, PUT"); //Make sure you remove those you do not want to support
if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_HEADERS"]))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
//Just exit with 200 OK with the above headers for OPTIONS method
exit(0);
}
//From here, handle the request as it is ok

CORS can become a headache, if we do not correctly understand its functioning. I use them in PHP and they work without problems. reference here
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 1000");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");
header("Access-Control-Allow-Methods: PUT, POST, GET, OPTIONS, DELETE");

This much code works down for me when using angular 4 as the client side and PHP as the server side.
header("Access-Control-Allow-Origin: *");

this should work
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");

I used these 5 headers and after that solved the cors error(backend: PHP, Frontend: VUE JS)
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS, post, get');
header("Access-Control-Max-Age", "3600");
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Access-Control-Allow-Credentials", "true");

add this code in .htaccess
add custom authentication key's in header like app_key,auth_key..etc
Header set Access-Control-Allow-Origin "*"
Header set Access-Control-Allow-Headers: "customKey1,customKey2, headers, Origin, X-Requested-With, Content-Type, Accept, Authorization"

enable Access-Control-Allow-Headers in codeigniter (issue related to ajax) [duplicate]

I have a simple PHP script that I am attempting a cross-domain CORS request:
<?php
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: *");
...
Yet I still get the error:
Request header field X-Requested-With is not allowed by Access-Control-Allow-Headers
Anything I'm missing?

Handling CORS requests properly is a tad more involved. Here is a function that will respond more fully (and properly).
/**
* An example CORS-compliant method. It will allow any GET, POST, or OPTIONS requests from any
* origin.
*
* In a production environment, you probably want to be more restrictive, but this gives you
* the general idea of what is involved. For the nitty-gritty low-down, read:
*
* - https://developer.mozilla.org/en/HTTP_access_control
* - https://fetch.spec.whatwg.org/#http-cors-protocol
*
*/
function cors() {
// Allow from any origin
if (isset($_SERVER['HTTP_ORIGIN'])) {
// Decide if the origin in $_SERVER['HTTP_ORIGIN'] is one
// you want to allow, and if so:
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400'); // cache for 1 day
}
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
// may also be using PUT, PATCH, HEAD etc
header("Access-Control-Allow-Methods: GET, POST, OPTIONS");
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
exit(0);
}
echo "You have CORS!";
}
Security Notes
Check the HTTP_ORIGIN header against a list of approved origins.
If the origin isn't approved, then you should deny the request.
Please read the spec.
TL;DR
When a browser wants to execute a cross-site request it first confirms that this is okay with a "pre-flight" request to the URL. By allowing CORS you are telling the browser that responses from this URL can be shared with other domains.
CORS does not protect your server. CORS attempts to protect your users by telling browsers what the restrictions should be on sharing responses with other domains. Normally this kind of sharing is utterly forbidden, so CORS is a way to poke a hole in the browser's normal security policy. These holes should be as small as possible, so always check the HTTP_ORIGIN against some kind of internal list.
There are some dangers here, especially if the data the URL serves up is normally protected. You are effectively allowing browser content that originated on some other server to read (and possibly manipulate) data on your server.
If you are going to use CORS, please read the protocol carefully (it is quite small) and try to understand what you're doing. A reference URL is given in the code sample for that purpose.
Header security
It has been observed that the HTTP_ORIGIN header is insecure, and that is true. In fact, all HTTP headers are insecure to varying meanings of the term. Unless a header includes a verifiable signature/hmac, or the whole conversation is authenticated via TLS, headers are just "something the browser has told me".
In this case, the browser is saying "an object from domain X wants to get a response from this URL. Is that okay?" The point of CORS is to be able to answer, "yes I'll allow that".

I got the same error, and fixed it with the following PHP in my back-end script:
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST');
header("Access-Control-Allow-Headers: X-Requested-With");

Access-Control-Allow-Headers does not allow * as accepted value, see the Mozilla Documentation here.
Instead of the asterisk, you should send the accepted headers (first X-Requested-With as the error says).
Update:
* is now accepted is Access-Control-Allow-Headers.
According to MDN Web Docs 2021:
The value * only counts as a special wildcard value for requests without credentials (requests without HTTP cookies or HTTP authentication information). In requests with credentials, it is treated as the literal header name * without special semantics. Note that the Authorization header can't be wildcarded and always needs to be listed explicitly.

Many description internet-wide don't mention that specifying Access-Control-Allow-Origin is not enough. Here is a complete example that works for me:
<?php
if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST, GET, DELETE, PUT, PATCH, OPTIONS');
header('Access-Control-Allow-Headers: token, Content-Type');
header('Access-Control-Max-Age: 1728000');
header('Content-Length: 0');
header('Content-Type: text/plain');
die();
}
header('Access-Control-Allow-Origin: *');
header('Content-Type: application/json');
$ret = [
'result' => 'OK',
];
print json_encode($ret);

I've simply managed to get dropzone and other plugin to work with this fix (angularjs + php backend)
header('Access-Control-Allow-Origin: *');
header("Access-Control-Allow-Credentials: true");
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS');
header('Access-Control-Max-Age: 1000');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token , Authorization');
add this in your upload.php or where you would send your request (for example if you have upload.html and you need to attach the files to upload.php, then copy and paste these 4 lines).
Also if you're using CORS plugins/addons in chrome/mozilla be sure to toggle them more than one time,in order for CORS to be enabled

If you want to create a CORS service from PHP, you can use this code as the first step in your file that handles the requests:
// Allow from any origin
if(isset($_SERVER["HTTP_ORIGIN"]))
{
// You can decide if the origin in $_SERVER['HTTP_ORIGIN'] is something you want to allow, or as we do here, just allow all
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
}
else
{
//No HTTP_ORIGIN set, so we allow any. You can disallow if needed here
header("Access-Control-Allow-Origin: *");
}
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 600"); // cache for 10 minutes
if($_SERVER["REQUEST_METHOD"] == "OPTIONS")
{
if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_METHOD"]))
header("Access-Control-Allow-Methods: POST, GET, OPTIONS, DELETE, PUT"); //Make sure you remove those you do not want to support
if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_HEADERS"]))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
//Just exit with 200 OK with the above headers for OPTIONS method
exit(0);
}
//From here, handle the request as it is ok

CORS can become a headache, if we do not correctly understand its functioning. I use them in PHP and they work without problems. reference here
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 1000");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");
header("Access-Control-Allow-Methods: PUT, POST, GET, OPTIONS, DELETE");

This much code works down for me when using angular 4 as the client side and PHP as the server side.
header("Access-Control-Allow-Origin: *");

this should work
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");

I used these 5 headers and after that solved the cors error(backend: PHP, Frontend: VUE JS)
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS, post, get');
header("Access-Control-Max-Age", "3600");
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Access-Control-Allow-Credentials", "true");

add this code in .htaccess
add custom authentication key's in header like app_key,auth_key..etc
Header set Access-Control-Allow-Origin "*"
Header set Access-Control-Allow-Headers: "customKey1,customKey2, headers, Origin, X-Requested-With, Content-Type, Accept, Authorization"

jQuery .get() :Rrequest to external API - Access error : Doesn't match

I have already taken a look at this link and cannot seem to find where my issue is even after constant debugging.
I know my .htaccess file works because it works for internal requests and the ReWrite is working as expected.
My current .htaccess code (on the API server) however is:
Header set Access-Control-Allow-Origin "*"
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^API/Public /API/Public/api.php [QSA,L]
My PHP file headers (on the API server) are:
// Allow from any origin
if (isset($_SERVER['HTTP_ORIGIN'])) {
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400'); // cache for 1 day
}
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
header("Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS");
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
}
However, I still get this error when I try now send a request to that API server:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://www.example.com/API/Public/?start=example. (Reason: CORS header 'Access-Control-Allow-Origin' does not match 'http://sendingfrom.com, *').
using this code:
$.get('http://www.example.com/API/Public/', { start: 'example' })
.done(function(test){
alert(test);
});
Could someone please offer me any help to where I have gone wrong or what I am missing? Thanks so much in advance!

Omg, I found the fix here.
I had to remove the whole PHP headers:
// Allow from any origin
if (isset($_SERVER['HTTP_ORIGIN'])) {
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400'); // cache for 1 day
}
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
header("Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS");
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
}

php session value is not working in chrome browser but working in postman?

i am working with RESTFUL APIs . my front-end(http://localhost:3000/) and back-end(http://workless/services) are in different origin. Because of that i have implemented the CORS mechanism to access the sevice from different origin.
it like bellows..
if (isset($_SERVER['HTTP_ORIGIN'])) {
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
// optional configuration
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400'); // cache for 1 day
}
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
header("Access-Control-Allow-Methods: GET, POST");
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
header("Access-Control-Allow-Headers:{$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
exit(0);
}
Everything is working on postman tools, trouble is while i'm going to call some apis which is needed saved session value it's return 401 status because of losing the session value..
The session value is not stored while accessing via chrome/mozilla but it's working on postman..
can anyone please say why it occurs??

Cross-Origin Request Headers(CORS) with PHP headers

I have a simple PHP script that I am attempting a cross-domain CORS request:
<?php
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: *");
...
Yet I still get the error:
Request header field X-Requested-With is not allowed by Access-Control-Allow-Headers
Anything I'm missing?

Handling CORS requests properly is a tad more involved. Here is a function that will respond more fully (and properly).
/**
* An example CORS-compliant method. It will allow any GET, POST, or OPTIONS requests from any
* origin.
*
* In a production environment, you probably want to be more restrictive, but this gives you
* the general idea of what is involved. For the nitty-gritty low-down, read:
*
* - https://developer.mozilla.org/en/HTTP_access_control
* - https://fetch.spec.whatwg.org/#http-cors-protocol
*
*/
function cors() {
// Allow from any origin
if (isset($_SERVER['HTTP_ORIGIN'])) {
// Decide if the origin in $_SERVER['HTTP_ORIGIN'] is one
// you want to allow, and if so:
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 86400'); // cache for 1 day
}
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
// may also be using PUT, PATCH, HEAD etc
header("Access-Control-Allow-Methods: GET, POST, OPTIONS");
if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
exit(0);
}
echo "You have CORS!";
}
Security Notes
Check the HTTP_ORIGIN header against a list of approved origins.
If the origin isn't approved, then you should deny the request.
Please read the spec.
TL;DR
When a browser wants to execute a cross-site request it first confirms that this is okay with a "pre-flight" request to the URL. By allowing CORS you are telling the browser that responses from this URL can be shared with other domains.
CORS does not protect your server. CORS attempts to protect your users by telling browsers what the restrictions should be on sharing responses with other domains. Normally this kind of sharing is utterly forbidden, so CORS is a way to poke a hole in the browser's normal security policy. These holes should be as small as possible, so always check the HTTP_ORIGIN against some kind of internal list.
There are some dangers here, especially if the data the URL serves up is normally protected. You are effectively allowing browser content that originated on some other server to read (and possibly manipulate) data on your server.
If you are going to use CORS, please read the protocol carefully (it is quite small) and try to understand what you're doing. A reference URL is given in the code sample for that purpose.
Header security
It has been observed that the HTTP_ORIGIN header is insecure, and that is true. In fact, all HTTP headers are insecure to varying meanings of the term. Unless a header includes a verifiable signature/hmac, or the whole conversation is authenticated via TLS, headers are just "something the browser has told me".
In this case, the browser is saying "an object from domain X wants to get a response from this URL. Is that okay?" The point of CORS is to be able to answer, "yes I'll allow that".

I got the same error, and fixed it with the following PHP in my back-end script:
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST');
header("Access-Control-Allow-Headers: X-Requested-With");

Access-Control-Allow-Headers does not allow * as accepted value, see the Mozilla Documentation here.
Instead of the asterisk, you should send the accepted headers (first X-Requested-With as the error says).
Update:
* is now accepted is Access-Control-Allow-Headers.
According to MDN Web Docs 2021:
The value * only counts as a special wildcard value for requests without credentials (requests without HTTP cookies or HTTP authentication information). In requests with credentials, it is treated as the literal header name * without special semantics. Note that the Authorization header can't be wildcarded and always needs to be listed explicitly.

Many description internet-wide don't mention that specifying Access-Control-Allow-Origin is not enough. Here is a complete example that works for me:
<?php
if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST, GET, DELETE, PUT, PATCH, OPTIONS');
header('Access-Control-Allow-Headers: token, Content-Type');
header('Access-Control-Max-Age: 1728000');
header('Content-Length: 0');
header('Content-Type: text/plain');
die();
}
header('Access-Control-Allow-Origin: *');
header('Content-Type: application/json');
$ret = [
'result' => 'OK',
];
print json_encode($ret);

I've simply managed to get dropzone and other plugin to work with this fix (angularjs + php backend)
header('Access-Control-Allow-Origin: *');
header("Access-Control-Allow-Credentials: true");
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS');
header('Access-Control-Max-Age: 1000');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token , Authorization');
add this in your upload.php or where you would send your request (for example if you have upload.html and you need to attach the files to upload.php, then copy and paste these 4 lines).
Also if you're using CORS plugins/addons in chrome/mozilla be sure to toggle them more than one time,in order for CORS to be enabled

If you want to create a CORS service from PHP, you can use this code as the first step in your file that handles the requests:
// Allow from any origin
if(isset($_SERVER["HTTP_ORIGIN"]))
{
// You can decide if the origin in $_SERVER['HTTP_ORIGIN'] is something you want to allow, or as we do here, just allow all
header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
}
else
{
//No HTTP_ORIGIN set, so we allow any. You can disallow if needed here
header("Access-Control-Allow-Origin: *");
}
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 600"); // cache for 10 minutes
if($_SERVER["REQUEST_METHOD"] == "OPTIONS")
{
if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_METHOD"]))
header("Access-Control-Allow-Methods: POST, GET, OPTIONS, DELETE, PUT"); //Make sure you remove those you do not want to support
if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_HEADERS"]))
header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
//Just exit with 200 OK with the above headers for OPTIONS method
exit(0);
}
//From here, handle the request as it is ok

CORS can become a headache, if we do not correctly understand its functioning. I use them in PHP and they work without problems. reference here
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 1000");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");
header("Access-Control-Allow-Methods: PUT, POST, GET, OPTIONS, DELETE");

This much code works down for me when using angular 4 as the client side and PHP as the server side.
header("Access-Control-Allow-Origin: *");

this should work
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");

I used these 5 headers and after that solved the cors error(backend: PHP, Frontend: VUE JS)
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS, post, get');
header("Access-Control-Max-Age", "3600");
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Access-Control-Allow-Credentials", "true");

add this code in .htaccess
add custom authentication key's in header like app_key,auth_key..etc
Header set Access-Control-Allow-Origin "*"
Header set Access-Control-Allow-Headers: "customKey1,customKey2, headers, Origin, X-Requested-With, Content-Type, Accept, Authorization"

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