php判断数据库是否连接成功的测试例子

<form action="" method="post">    <select name="host">        <option value="localhost" selected>localhost</option>        <option value="127.0.0.1">127.0.0.1</option>    </select>    <br><br>    user:<input type="text" name="user" value=""><br><br>    pwd :<input type="passWord" name="pwd" value=""><br><br>    <input type="submit" value="connent">    <input type="reset" value="reset"></form><?php     error_reporting(~E_ALL);    $host = $_POST['host'];    $user = $_POST['user'];    $pwd = $_POST['pwd'];    if(isset($_POST['host']) && isset($_POST['user']) && isset($_POST['pwd'])){        if(strlen($host)<1 or strlen($user)<1 or strlen($pwd)<1){            echo "请完善相关数据库链接信息。";            exit(0);        }        $conn = mysql_connect($host, $user, $pwd) or die("Error-数据库连接失败！");        if($conn){            echo "OK—数据库连接成功！";        }    }?>