this code to try php sign in,

PHP apple sign in

<?php

/**
 * This file to test apple sign in,
 * Need to app information from Apple
 * 
 * Team Id
 * Client Id
 * Key Id
 * and Private key
 * 
 * and from App need to use code
 * 
 * Note: Some of this codde is taken from firebase JWT library, I just copy&paste to make 
 * this code runnable withouy any dependency
 * 
 */
const TEAM_ID = 'XXXXXXXXXX';
const CLIENT_ID = 'com.XXXXXXXX.App';
const KEY_ID = 'XXXXXXXXXX';

$key = <<<KEY
-----BEGIN PRIVATE KEY-----
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXX
-----END PRIVATE KEY-----
KEY;


$ecdsa_key = openssl_pkey_get_private($key);

$header = array('typ' => 'JWT', 'alg' => 'ES256');
$header['kid'] = KEY_ID;


$payload = [
    'iss' => TEAM_ID,
    'iat' => time(),
    'exp' => time() + 86400*180,
    'aud' => 'https://appleid.apple.com',
    'sub' => CLIENT_ID,
];

$segments = array();
$segments[] = urlsafeB64Encode(json_encode($header));
$segments[] = urlsafeB64Encode(json_encode($payload));
$signing_input = \implode('.', $segments);
$signature = '';

$success = \openssl_sign($signing_input, $signature, $key, 'SHA256');
if (!$success) {
    throw new DomainException("OpenSSL unable to sign data");
} else {
    if ($header['alg'] === 'ES256') {
        $signature = signatureFromDER($signature, 256);
    }
}

$segments[] = urlsafeB64Encode($signature);

$clientSecret = \implode('.', $segments);



$code = 'CODE GENERATED FROM APP';
$curl = curl_init();
$postData = [
    "client_id=CLIENT_ID",
    "client_secret=$clientSecret",
    "code=$code",
    "grant_type=authorization_code"
];


curl_setopt_array($curl, array(
    CURLOPT_URL => "https://appleid.apple.com/auth/token",
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 0,
    CURLOPT_FOLLOWLOCATION => true,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_POSTFIELDS => implode('&', $postData),
));

$response = curl_exec($curl);

curl_close($curl);

echo $response;

function urlsafeB64Encode($input)
{
    return \str_replace('=', '', \strtr(\base64_encode($input), '+/', '-_'));
}

function signatureFromDER($der, $keySize)
{

    // OpenSSL returns the ECDSA signatures as a binary ASN.1 DER SEQUENCE
    list($offset, $_) = readDER($der);
    list($offset, $r) = readDER($der, $offset);
    list($offset, $s) = readDER($der, $offset);

    // Convert r-value and s-value from signed two's compliment to unsigned
    // big-endian integers
    $r = \ltrim($r, "\x00");
    $s = \ltrim($s, "\x00");

    // Pad out r and s so that they are $keySize bits long
    $r = \str_pad($r, $keySize / 8, "\x00", STR_PAD_LEFT);
    $s = \str_pad($s, $keySize / 8, "\x00", STR_PAD_LEFT);

    return $r . $s;
}



function readDER($der, $offset = 0)
{
    $ASN1_BIT_STRING = 0x03;

    $pos = $offset;
    $size = \strlen($der);
    $constructed = (\ord($der[$pos]) >> 5) & 0x01;
    $type = \ord($der[$pos++]) & 0x1f;

    // Length
    $len = \ord($der[$pos++]);
    if ($len & 0x80) {
        $n = $len & 0x1f;
        $len = 0;
        while ($n-- && $pos < $size) {
            $len = ($len << 8) | \ord($der[$pos++]);
        }
    }

    // Value
    if ($type == $ASN1_BIT_STRING) {
        $pos++; // Skip the first contents octet (padding indicator)
        $data = \substr($der, $pos, $len - 1);
        $pos += $len - 1;
    } elseif (!$constructed) {
        $data = \substr($der, $pos, $len);
        $pos += $len;
    } else {
        $data = null;
    }

    return array($pos, $data);
}

Yes, that's right.

https://sarunw.com/posts/sign-in-with-apple-3/

$key is constantly changing, you can't hardcode it, that's why this doesn't work.

Hi @ameen-sarsour
I am getting error {"error":"invalid_client"}

Hi @ameen-sarsour

• and from App need to use code
  Is this code generated from flutter app appleCredential.identityToken

I am getting error {"error":"invalid_client"}

me too invalid_client
if o create the client_id on ruby it works but client_id created on php doesnt works!

me too invalid_client . I am using this code and create client_secret but show this error

Client error: POST https://appleid.apple.com/auth/token resulted in a 400 Bad Request response: {"error":"invalid_client","email_verified":false}