Creates a fallback for those not using PHP 5.4, however requires you use jsonEncode() not json_encode

jsonEncodeFallback.php

<?php

	if (PHP_VERSION >= 50400) {

		function jsonEncode(){
			return call_user_func_array('json_encode', (array)func_get_args());
		}
	}else{

		interface JsonSerializable{
			public function jsonSerialize();
		}

		function jsonEncode(){
			$args = func_get_args();

			if(count($args) > 0){

				if(!is_object($args[0])){
					return call_user_func_array('json_encode', (array)func_get_args());
				}

				try{
					$value = array_shift($args);
					$class = new ReflectionClass($value);

					if($class->implementsInterface('JsonSerializable')){
						array_unshift($args, $value->jsonSerialize());

						return call_user_func_array('json_encode', $args); 
					}
				}catch(Exception $e){

				}
			}

			if(function_exists('json_last_error')){
				switch (json_last_error()) {
					case JSON_ERROR_DEPTH:
						throw new RuntimeException('Maximum stack depth exceeded', null, ((isset($e) ? $e : null)));
					case JSON_ERROR_STATE_MISMATCH:
						throw new RuntimeException('Underflow or the modes mismatch', null, ((isset($e) ? $e : null)));
					case JSON_ERROR_CTRL_CHAR:
						throw new RuntimeException('Unexpected control character found', null, ((isset($e) ? $e : null)));
					case JSON_ERROR_SYNTAX:
						throw new RuntimeException('Syntax error, malformed JSON', null, ((isset($e) ? $e : null)));
					case JSON_ERROR_UTF8:
						throw new RuntimeException('Malformed UTF-8 characters, possibly incorrectly encoded', null, ((isset($e) ? $e : null)));
					default:
						throw new RuntimeException('Unknown Error', null, ((isset($e) ? $e : null)));
				}
			}

			throw new RuntimeException('Your JSON is fucked, no json_last_error() either...');
		}

	}

	class Piss implements JsonSerializable
	{
		private $_bullshit;
		private $_moreBullshit;

		public function __construct()
		{
			$this->_bullshit = range(1,10);
		}

		public function jsonSerialize()
		{
			return $this->_bullshit;
		}
	}

	echo jsonEncode(array('a' => 1));
	echo jsonEncode(new Piss());