function GetCurrentMinutes($WithZero)
{ $minutes=getdate(time());
  $minutes=$minutes["minutes"];
  if ($WithZero)  { if ($minutes<10) {$minutes="0".$minutes;}  }
  return $minutes;
}
function GetCurrentHours($WithZero)
{ $hours=getdate(time());  $hours=$hours["hours"];
   if ($WithZero)  { if ($hours<10) {$hours="0".$hours;} }
 return $hours;
}
  $hour=GetCurrentHours(1);
  $min=GetCurrentMinutes(1);
  $min=round($min/5)*5;
  $time=$hour.":".$min.":00";

 The function getdate () in any moment (arising very seldom) returns values 0 hours and 0 minutes accordingly 
I tested the given function "rolling" her(it) in cycle from 1 up to 10000. There was no error. But in substantial script 
The error unfortunately arises. By a variable $time the value is assigned only once. She(it) is more anywhere 
The variable $time is reassigned and still in any of the appeals to script receives equal 00:00:00