Add class for validating color codes

MD_STD_IN.php

@@ -85,6 +85,27 @@ final class MD_STD_IN {
 
     }
 
+    /**
+     * String sanitization for 3 o4 6 characters RGB color codes (sans the leading #).
+     *
+     * @param mixed $input Input string.
+     *
+     * @return string
+     */
+    public static function sanitize_rgb_color($input):string {
+
+        $output = \filter_var($input,
+            FILTER_SANITIZE_STRING,
+            FILTER_FLAG_NO_ENCODE_QUOTES);
+
+        if (!(preg_match('/^[a-zA-Z0-9]{3}$/', $output)) && !(preg_match('/^[a-zA-Z0-9]{6}$/', $output))) {
+            throw new MDInvalidColorCode("Invalid color code provided: " . $output);
+        }
+
+        return $output;
+
+    }
+
     /**
      * Retrieves HTTP input texts from GET or POST variables, whatever is provided.
      * If neither is given, returns a provided default.