require all necessary psr implementations

the code relies on psr7, psr17 and psr18 implementations to be available, with the discovery.

it no longer uses the php-http httplug interface (which was made obsolete by psr-18). php-http/client-common is also not used in the code.

README.md

@@ -14,17 +14,13 @@ There are two ways to use MailerLite PHP SDK:
 
 If you are not familiar with Composer, learn about it [here](https://getcomposer.org/doc/01-basic-usage.md).
 
-Then you will need to run this simple command using CLI:
-
-```
-composer require mailerlite/mailerlite-api-v2-php-sdk
-```
-
 This library is built atop of [PSR-7](https://www.php-fig.org/psr/psr-7/) and
-[PSR-18](https://www.php-fig.org/psr/psr-18/). If you are receiving `Http\Discovery\Exception\DiscoveryFailedException` exception, you will need to run:
+[PSR-18](https://www.php-fig.org/psr/psr-18/).
+
+To install the library, you also need to choose an HTTP client implementation. To install the mailerlite with guzzle, run this command line:
 
-```bash
-composer require php-http/guzzle6-adapter
+```
+composer require mailerlite/mailerlite-api-v2-php-sdk guzzlehttp/guzzle
 ```
 
 ##### Manual (preferable for shared hostings)

composer.json

@@ -7,13 +7,14 @@
     "type": "library",
     "require": {
         "php" : "^7.1 || ^8.0",
-        "php-http/client-common": "^2.0",
+        "psr/http-message-implementation": "*",
+        "psr/http-factory-implementation": "*",
+        "psr/http-client-implementation": "*",
         "php-http/discovery": "^1.7",
-        "nyholm/psr7": "^1.0",
         "ext-json": "*"
     },
     "require-dev": {
-        "php-http/guzzle6-adapter": "^2.0",
+        "guzzlehttp/guzzle": "^7.0",
         "phpunit/phpunit": "6.* | 7.* | 8.* | 9.*"
     },
     "autoload": {
@@ -25,5 +26,8 @@
         "psr-4": {
             "MailerLiteApi\\Tests\\": "tests/"
         }
+    },
+    "conflict": {
+        "php-http/httplug": "< 2"
     }
 }

src/Common/RestClient.php

@@ -2,7 +2,6 @@
 
 namespace MailerLiteApi\Common;
 
-use Http\Client\HttpClient;
 use Http\Discovery\Psr17FactoryDiscovery;
 use Http\Discovery\Psr18ClientDiscovery;
 use Psr\Http\Client\ClientInterface;
@@ -25,9 +24,9 @@ class RestClient {
     /**
      * @param  string  $baseUrl
      * @param  string  $apiKey
-     * @param  \Http\Client\HttpClient|null  $httpClient
+     * @param  ClientInterface|null  $httpClient
      */
-    public function __construct($baseUrl, $apiKey, HttpClient $httpClient = null)
+    public function __construct($baseUrl, $apiKey, ClientInterface $httpClient = null)
     {
         $this->baseUrl = $baseUrl;
         $this->apiKey = $apiKey;

src/MailerLite.php

@@ -2,11 +2,10 @@
 
 namespace MailerLiteApi;
 
-use Http\Client\HttpClient;
-
 use MailerLiteApi\Common\ApiConstants;
 use MailerLiteApi\Common\RestClient;
 use MailerLiteApi\Exceptions\MailerLiteSdkException;
+use Psr\Http\Client\ClientInterface;
 
 /**
  * Class MailerLite
@@ -27,11 +26,11 @@ class MailerLite {
 
     /**
      * @param string|null $apiKey
-     * @param HttpClient $client
+     * @param ClientInterface|null $client
      */
     public function __construct(
         $apiKey = null,
-        HttpClient $httpClient = null
+        ClientInterface $httpClient = null
     ) {
         if (is_null($apiKey)) {
             throw new MailerLiteSdkException("API key is not provided");