使用mysqli_connect和mysql_select_db

Question

此代碼正常工作！

$con=mysqli_connect("localhost","root","","laboratory"); 
// Check connection 
if (mysqli_connect_errno()) 
    { 
    echo "Failed to connect to MySQL: " . mysqli_connect_error(); 
    } 

$result = mysqli_query($con,"SELECT * FROM test"); 

while($row = mysqli_fetch_array($result)) 
    { 
    echo $row['name']; 
    echo "<br>"; 
    } 

mysqli_close($con); 

但是當我刪除數據庫名稱從mysqli_connect我會用通過mysql_select_db，出現以下錯誤：「警告：mysql_select_db（）預計參數2是資源，目標在給定的」改變後

代碼：

$con=mysqli_connect("localhost","root",""); 
// Check connection 
if (mysqli_connect_errno()) 
    { 
    echo "Failed to connect to MySQL: " . mysqli_connect_error(); 
    } 

$db_selected = mysql_select_db("laboratory", $con); 

if (!$db_selected) 
    { 
    die ("Can\'t use laboratory : " . mysql_error()); 
    } 

$result = mysqli_query($con,"SELECT * FROM test"); 

while($row = mysqli_fetch_array($result)) 
    { 
    echo $row['name']; 
    echo "<br>"; 
    } 

mysqli_close($con); 

Answer 1

請不要混合mysqli和mysql，因爲它們是不同的模塊。

在您的第二個代碼塊中，您使用的是mysql_select_db和mysql_error，第一個需要連接mysql，而不是mysqli連接。

Answer 2

更換你的代碼：* mysqli的資源

$db_selected = mysqli_select_db("laboratory", $con);，而不是

$db_selected = mysql_select_db("laboratory", $con);