provide content-type matching ability for activitypub

include/network.php

@@ -1896,3 +1896,41 @@ function service_plink($contact, $guid) {
 	return $x['plink'];
 }
 
+function getBestSupportedMimeType($mimeTypes = null, $acceptedTypes = false) {
+    // Values will be stored in this array
+
+	if($acceptedTypes === false)
+		$acceptedTypes = $_SERVER['HTTP_ACCEPT'];
+
+    $AcceptTypes = Array ();
+
+    // Accept header is case insensitive, and whitespace isn’t important
+    $accept = strtolower(str_replace(' ', '', $acceptedTypes));
+    // divide it into parts in the place of a ","
+    $accept = explode(',', $accept);
+    foreach ($accept as $a) {
+        // the default quality is 1.
+        $q = 1;
+        // check if there is a different quality
+        if (strpos($a, ';q=')) {
+            // divide "mime/type;q=X" into two parts: "mime/type" i "X"
+            list($a, $q) = explode(';q=', $a);
+        }
+        // mime-type $a is accepted with the quality $q
+        // WARNING: $q == 0 means, that mime-type isn’t supported!
+        $AcceptTypes[$a] = $q;
+    }
+    arsort($AcceptTypes);
+
+    // if no parameter was passed, just return parsed data
+    if (!$mimeTypes) return $AcceptTypes;
+
+    $mimeTypes = array_map('strtolower', (array)$mimeTypes);
+
+    // let’s check our supported types:
+    foreach ($AcceptTypes as $mime => $q) {
+       if ($q && in_array($mime, $mimeTypes)) return $mime;
+    }
+    // no mime-type found
+    return null;
+}