PHP:已连接到数据库，但 mysql_query 失败

Question

我在开始学习 PHP 时遇到了非常奇怪的问题。我已经在 MySQL 数据库中创建了包含一些数据的表，现在我想在网页中显示它们。

这是我遇到此问题的来源:

<?php
    // Here I open connection
    $con = mysql_connect("localhost","root","aaaaaa");
    // set the mysql database
    $db = mysql_select_db("infs", $con);

    // I check the connection
    if (mysqli_connect_errno())
    {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }
    else {
        // It always goes here
        echo "Connected to database!";
    }

    // I am testing very simple SQL query.. there should be no problem
    $result = mysql_query("SELECT * FROM cathegories", $con, $db);

    if (!$result) {
        // but it always dies
        $message  = 'Invalid query: ' . mysql_error() . "\n";
        $message .= 'Whole query: ' . $query;
        die($message);
    }

    mysql_close($con);
?>

出了什么问题？

提前致谢!

Answer 1

您正在混合 mysql 和 mysqli。 尝试这样的事情:

<?php   
    $con= new mysqli("localhost","user","passwd","database");
    if ($con->connect_errno){
      echo "could not connect";
    }

    $select = "SELECT * FROM tablename";

    if($result = $con->query($select)){
        while($row = $result->fetch_object()){
            echo $row->rowname."<br>";
        }
    }
    else { echo 'no result'; }
    $con->close();  
?>