Add a way to manage fallbacks for not implemented functions.

Raise warning if try to use json_encode() when it's not available. PHP 5 < PHP 5.2.0 doesn't provide json functions natively.

lib/limonade.php

@@ -373,6 +373,7 @@ function run($env = null)
 
   # 3. Loading libs
   require_once_dir(option('lib_dir'));
+  fallbacks_for_not_implemented_functions();
 
   # 4. Starting session
   if(!defined('SID') && option('session'))
@@ -1547,7 +1548,9 @@ function txt($content_or_func, $layout = '', $locals = array())
 }
 
 /**
- * Returns json representation of data with proper http headers
+ * Returns json representation of data with proper http headers.
+ * On PHP 5 < PHP 5.2.0, you must provide your own implementation of the
+ * <code>json_encode()</code> function beore using <code>json()</code>.
  *
  * @param string $data 
  * @param int $json_option
@@ -2637,5 +2640,28 @@ function htmlspecialchars_decode($string, $quote_style = ENT_COMPAT)
 	}
 }
 
+/**
+ * Called just after loading libs, it provides fallback for some 
+ * functions if they don't exists.
+ *
+ */
+function fallbacks_for_not_implemented_functions()
+{
+  if(!function_exists('json_encode'))
+  {
+    /**
+     * for PHP 5 < PHP 5.2.0
+     *
+     */
+    function json_encode()
+    {
+      trigger_error(
+        __FUNCTION__ . '(): no JSON functions available. Please provide your own implementation of ' . __FUNCTION__ . '() in order to use it.', E_USER_WARNING
+      );
+    }
+  }
+}
+
+
 
 #   ================================= END ==================================   #