如何隔离可能包含空格的空格分隔值？

I have an input where a user will enter a class schedule in the following format

[time] [days] [room]

e.g:

7-8 am MWF ROOM1 | 7:30-9:30 am TTH Room2 | 11:30 am-12:30 pm MWF Room3)

So I tried exploding the input using space then get the last two values of the returned array and make the as $room and $days, then I subtracted the two in the original $schedule to get the remaining and make it my $time.

$sched = explode(" ", $schedule);
if(count($sched) <= 3){
    echo 'please check schedule format!';
}else{
   $room  = array_values(array_slice($sched, -1))[0];
   $days  = array_values(array_slice($sched, -2))[0];
   $times = str_replace($days." ".$room, "" ,$schedule);
}

using the code above I'm getting the result I want, but the problem is when the user does not put DAYS or ROOM the text adjusts so I'm not getting the right value.

For example this input value

11:30 am-12:30 pm mwf (no room)

I'm getting this result: (room:mwf) (days:pm) (times:11:30 am-12:30 )

Is there better way to this?

This pattern will process the full string and spit out a multi-dimensional array. How do you want to handle the results?

Test Code: (Demo)

//$sched='7-8 am MWF ROOM1 | 7:30-9:30 am TTH Room2 | 11:30 am-12:30 pm MWF Room3';
$sched='MWF ROOM1 | 7:30-9:30 am Room2 | 11:30 am-12:30 pm MWF';
//$sched='ROOM1 | 7:30-9:30 am | MWF | MTWTHFS';

if(preg_match_all('/(?:^|\| )([^|]*?m)? ?([MTWHFS]*) ?([Rr][Oo]{2}[Mm]\d+)?(?: |$)/',$sched,$out,PREG_SET_ORDER)){
    foreach($out as $a){
        if(empty($a[1])){
            echo "Missing/Invalid Time
";
        }
        if(empty($a[2])){
            echo "Missing/Invalid Days
";
        }
        if(empty($a[3])){
            echo "Missing/Invalid Room
";
        }
        var_export(array_slice($a,1));
        echo"

";
    }
}

Output:

Missing/Invalid Time
array (
  0 => '',
  1 => 'MWF',
  2 => 'ROOM1',
)

Missing/Invalid Days
array (
  0 => '7:30-9:30 am',
  1 => '',
  2 => 'Room2',
)

Missing/Invalid Room
array (
  0 => '11:30 am-12:30 pm',
  1 => 'MWF',
)