但你可以做类似的事情：

$a = array('leg1'=>'LA','leg4'=>'FL');

$keys = array_keys($a);
foreach(array_keys($keys) AS $k ){
    $this_value = $a[$keys[$k]];
    $nextval = $a[$keys[$k+1]];
    $nextnextval = $a[$keys[$k+2]];

    if($nextval == $this_value && $nextnextval == $this_value){
       //staying put for next two legs
    }
}