static public function elapsedMemory($start, $end, $real_usage = false, $inMB = true) {
        $start = isset(self::$_marks[$start]) ? self::$_marks[$start]['memory_usage'] : 0;
        $end = isset(self::$_marks[$end]) ? self::$_marks[$end]['memory_usage'] : 0;
        
        $elapsed = !$real_usage ? ($end - $start) : $end;
        
        return $start ? ($inMB ? (($elapsed / 1024 / 1024) . ' MB') : $elapsed) : null;
    }
static public function elapsedMemory($start, $end, $real_usage = false, $inMB = true) {
        $start = isset(self::$_marks[$start]) ? self::$_marks[$start]['memory_usage'] : 0;
        $end = isset(self::$_marks[$end]) ? self::$_marks[$end]['memory_usage'] : 0;
        
        $elapsed = !$real_usage ? ($end - $start) : $end;
        
        return $start ? ($inMB ? (($elapsed / 1024 / 1024) . ' MB') : $elapsed) : null;
    }
static public function elapsedMemory ( $ start , $ end , $ real_usage = false , $ inMB = true ) { $ start = isset ( self :: $ _marks [ $ start ] ) ? self :: $ _marks [ $ start ] [ 'memory_usage' ] : 0 ; $ end = isset ( self :: $ _marks [ $ end ] ) ? self :: $ _marks [ $ end ] [ 'memory_usage' ] : 0 ; $ elapsed = ! $ real_usage ? ( $ end - $ start ) : $ end ; return $ start ? ( $ inMB ? ( ( $ elapsed / 1024 / 1024 ) . ' MB' ) : $ elapsed ) : null ; }
Get elapsed memory between two marks

@access  public
@param   string  $start  Start mark
@param   string  $end    End mark
@param   bool    $real_usage Get real memory usage
@param   bool    $inMB   Show output in MB instead of Bytes
@return  mixed   <string> if $inMB is <true>, <longint> if on <false>
Get elapsed memory between two marks