Add default_headers option

Author: jwilsson

docs/examples/setting-options.md

@@ -5,6 +5,7 @@ There are a few options that can be used to control the behaviour of the API. Al
 ```php
 $options = [
     'auto_refresh' => true,
+    'default_headers' => ['Accept-Language' => 'en-US'],
 ];
 
 // Options can be set using the SpotifyWebAPI constructor
@@ -28,6 +29,12 @@ Used to control [automatic refresh of access tokens](refreshing-access-tokens.md
 
 Used to control automatic retries of [rate limited requests](https://developer.spotify.com/documentation/web-api/guides/rate-limits/).
 
+### `default_headers`
+
+* Possible values: `[]` (default)
+
+Used to set default HTTP headers that will be included in every request. For example `Accept-Language` to force Latin alphabet in returned results. Passed as key-value pairs, e.g. `['Accept-Language' => 'en-US']`.
+
 ### `return_assoc`
 
 * Possible values: `true`/`false` (default)

src/Request.php

@@ -12,6 +12,7 @@ class Request
     protected array $lastResponse = [];
     protected array $options = [
         'curl_options' => [],
+        'default_headers' => [],
         'return_assoc' => false,
     ];
 
@@ -26,6 +27,25 @@ public function __construct(array|object $options = [])
         $this->setOptions($options);
     }
 
+    /**
+     * Format request headers to be used with cURL.
+     *
+     * @param array|object $headers The headers to format.
+     *
+     * @return array The formatted headers.
+     */
+    protected function formatHeaders(array|object $headers): array
+    {
+        $headers = array_merge((array) $this->options['default_headers'], $headers);
+
+        $formattedHeaders = [];
+        foreach ($headers as $key => $val) {
+            $formattedHeaders[] = "$key: $val";
+        }
+
+        return $formattedHeaders;
+    }
+
     /**
      * Handle response errors.
      *
@@ -181,21 +201,16 @@ public function send(string $method, string $url, string|array|object $parameter
             $parameters = http_build_query($parameters, '', '&');
         }
 
+        $method = strtoupper($method);
         $options = [
             CURLOPT_CAINFO => __DIR__ . '/cacert.pem',
             CURLOPT_ENCODING => '',
             CURLOPT_HEADER => true,
-            CURLOPT_HTTPHEADER => [],
+            CURLOPT_HTTPHEADER => $this->formatHeaders($headers),
             CURLOPT_RETURNTRANSFER => true,
             CURLOPT_URL => rtrim($url, '/'),
         ];
 
-        foreach ($headers as $key => $val) {
-            $options[CURLOPT_HTTPHEADER][] = "$key: $val";
-        }
-
-        $method = strtoupper($method);
-
         switch ($method) {
             case 'DELETE': // No break
             case 'PUT':

src/SpotifyWebAPI.php

@@ -11,6 +11,7 @@ class SpotifyWebAPI
     protected array $options = [
         'auto_refresh' => false,
         'auto_retry' => false,
+        'default_headers' => [],
         'return_assoc' => false,
     ];
     protected ?Request $request = null;
@@ -113,6 +114,7 @@ protected function sendRequest(
         array $headers = []
     ): array {
         $this->request->setOptions([
+            'default_headers' => $this->options['default_headers'],
             'return_assoc' => $this->options['return_assoc'],
         ]);