Fix Guzzle InvalidArgumentException for POST with array parameters

src/Network/HTTPClient/Capability/ICanSendHttpRequests.php

@@ -92,7 +92,7 @@ interface ICanSendHttpRequests
 	 * Send POST request to an URL
 	 *
 	 * @param string $url            URL to post
-	 * @param mixed  $params         array of POST variables
+	 * @param mixed  $params         POST variables (if an array is passed, it will automatically set as formular parameters)
 	 * @param array  $headers        HTTP headers
 	 * @param int    $timeout        The timeout in seconds, default system config value or 60 seconds
 	 *
@@ -107,6 +107,7 @@ interface ICanSendHttpRequests
 	 * @param string $url            Url to send to
 	 * @param array  $opts           (optional parameters) associative array with:
 	 *                       	      'body' => (mixed) setting the body for sending data
+	 *                       	      'form_params' => (array) Associative array of form field names to values
 	 *                                'accept_content' => (string array) supply Accept: header with 'accept_content' as the value
 	 *                                'timeout' => int Timeout in seconds, default system config value or 60 seconds
 	 *                                'cookiejar' => path to cookie jar file

src/Network/HTTPClient/Client/HttpClient.php

@@ -140,6 +140,10 @@ class HttpClient implements ICanSendHttpRequests
 			$conf[RequestOptions::BODY] = $opts[HttpClientOptions::BODY];
 		}
 
+		if (!empty($opts[HttpClientOptions::FORM_PARAMS])) {
+			$conf[RequestOptions::FORM_PARAMS] = $opts[HttpClientOptions::FORM_PARAMS];
+		}
+
 		if (!empty($opts[HttpClientOptions::AUTH])) {
 			$conf[RequestOptions::AUTH] = $opts[HttpClientOptions::AUTH];
 		}
@@ -205,7 +209,11 @@ class HttpClient implements ICanSendHttpRequests
 	{
 		$opts = [];
 
-		$opts[HttpClientOptions::BODY] = $params;
+		if (!is_array($params)) {
+			$opts[HttpClientOptions::BODY] = $params;
+		} else {
+			$opts[HttpClientOptions::FORM_PARAMS] = $params;
+		}
 
 		if (!empty($headers)) {
 			$opts[HttpClientOptions::HEADERS] = $headers;

src/Network/HTTPClient/Client/HttpClientOptions.php

@@ -59,9 +59,13 @@ class HttpClientOptions
 	const VERIFY = 'verify';
 
 	/**
-	 * body: (mixed) Setting the body for sending data
+	 * body: (string) Setting the body for sending data
 	 */
 	const BODY = RequestOptions::BODY;
+	/**
+	 * form_params: (array) Associative array of form field names to values
+	 */
+	const FORM_PARAMS = RequestOptions::FORM_PARAMS;
 	/**
 	 * auth: (array) Authentication settings for specific requests
 	 */