Execute PHP Online

<?php
$start="07:00:00";
$end="17:00:00";

$b=array(
    array('start'=>"07:00:00",'end'=>'07:30:00'),
    array('start'=>"08:45:00",'end'=>'09:00:00'),
    array('start'=>"10:00:00",'end'=>'10:15:00'),
    
);

$sp=array();
$loop=$start;
while($loop <= $end) {
   
	array_push($sp,$loop);
	$loop=date('H:i:s',strtotime('+15 minute',strtotime($loop)));
}

for($i=0;$i<count($b);$i++){
    $loop =	$b[$i]['start'];
	$app15array=array();
	while($loop <= $b[$i]['end']) {
		array_push($app15array,$loop);
		$loop=date('H:i:s',strtotime('+15 minute',strtotime($loop)));
	}
    $minus=$app15array;
    print_r($minus);
    //***************
    $loop=$minus[0];
    $tmp= (count($minus));
    var_dump((string)$tmp);
    while($loop <= $minus[2]){
        echo "yes";
        if(count($minus)==2){
            if(in_array($minus[0],$sp,TRUE)){
                array_splice($sp, array_search($minus[0],$sp), 1);
            }
        }
        if(count($minus)==3){
            if(in_array($minus[0],$sp,TRUE)){
                array_splice($sp, array_search($minus[0],$sp), 2);
            }
        }
        $loop=date('H:i:s',strtotime('+15 minute',strtotime($loop)));
    }
    //****************
}
echo "<pre>";
print_r($sp);