What is the difference between using empty to determine whether a variable is empty in PHP and directly writing it in the if condition?

$searchUrl = 'http://203.156.244.227:80/cgi...';

<code>if(!empty($_GET['content']))  
{  
    $searchUrl .= $_GET['content'];  
}  

    if($_GET['content'])  
{  
    $searchUrl .= $_GET['content'];  
} 
这两个判断有区别吗？</code>