PHP select MySQL给出未知错误

Question

我碰到一个问题，即时通讯尝试的PHP脚本。所以当我启动它时，脚本完美地连接到MySQL和数据库，但是当我尝试从'代码'数据库中选择数据时，它会给我一个这样的错误：“无法获取数据：”。它应该做的是说“无法获取数据:(然后是错误）”，但它没有。先谢谢了。 :)

PHP代码：

<?php 
$servername = "localhost"; 
$username = "username"; 
$password = "password"; 
$dbname = "database"; 

// Create connection 
$conn = mysqli_connect($servername, $username, $password); 
mysqli_select_db($dbname); 

// Check connection 
if (!$conn) { 
    die("Connection failed: " . mysqli_connect_error()); 
} 
echo "Connected successfully"; 

    $sql = 'SELECT code FROM codes'; 
    $retval = mysql_query($sql, $conn); 

    if(! $retval) { 
     die('Could not get data: ' . mysql_error()); 
    } 

    while($row = mysql_fetch_array($retval, MYSQL_ASSOC)) { 
     echo "Code:{$row['code']}"; 
    } 

    echo "Fetched data successfully\n"; 

    mysql_close($conn); 
?> 

Answer 1

你混合MySQL和mysqli的在一起，我固定的错误：

<?php 
ini_set('display_errors', 1); 
error_reporting(E_ALL); 
$servername = "localhost"; 
$username = "root"; 
$password = "pass"; 
$dbname = "table"; 

// Create connection 
$conn = mysqli_connect($servername, $username, $password); 
     mysqli_select_db($conn, $dbname); 

// Check connection 
if (!$conn) { 
    die("Connection failed: " . mysqli_connect_error()); 
} 
// echo "Connected successfully"; 

    $sql = 'SELECT username FROM users'; 
    $retval = mysqli_query($conn ,$sql); 

    if(! $retval) { 
     die('Could not get data: ' . mysqli_error()); 
    } 

    while($row=mysqli_fetch_array($retval,MYSQLI_ASSOC)) { 
     echo "Code:{$row['username']}"; 
    } 

    echo "Fetched data successfully\n"; 

    mysqli_close($conn); 
?>