吴裕雄--天生自然 PHP开发学习：条件语句

<?php  
$t=date("H");  
if ($t<"20")  
{  
    echo "Have a good day!";  
}  
?>  

<?php  
$t=date("H");  
if ($t<"10")  
{  
    echo "Have a good morning!";  
}  
elseif ($t<"20")  
{  
    echo "Have a good day!";  
}  
else  
{  
    echo "Have a good night!";  
}  
?>