将我已弃用的​​ mysql 转换为 mysqli

Question

我是这里的初学者，我需要学习从mysql 转换为mysqli 的基础知识。我想先从配置开始。我已经使用了这个 connect.php，它现在正在工作我想切换到不推荐使用的 mysqli。请告诉我如何修改这个脚本。

<?php
$host = "localhost";
$dbusername = "root";
$dbpassword = "nopassword";
$dbname = "student";

$link_id = mysql_connect($host, $dbusername, $dbpassword);
if(!$link_id){
    die(mysql_error("Can`t Connect To database")); 
}
else{
    $db = mysql_select_db($dbname, $link_id);
}     
if(!$db){
    die(mysql_error("Can`t select database")); 
}     
return;

?>

Answer 1

根据我的评论......

你可以这样做

$host       = "localhost";
$dbusername = "root";
$dbpassword = "nopassword";
$dbname     = "student";

$link = mysqli_connect($host,$dbusername,$dbpassword,$dbname) or die("Error " . mysqli_error($link)); 

$query   = "SELECT knowhow FROM google WHERE myknowhow='leaks'";
$knowhow = mysqli_query($link, $query); 

这只是您可以做到的最简单的方法。

但你应该这样使用它（OOP）

$db      = new mysqli($host,$dbusername,$dbpassword,$dbname);
$knowhow = $db->query("SELECT knowhow FROM google WHERE myknowhow='leaks'");

根据您的评论：

您不再需要 IF/ELSE 语句。

捕获所有错误

die("Error " . mysqli_error($link));

在oop中，错误被捕获

... new mysqli($host,$dbusername,$dbpassword,$dbname);

编辑

由于您被阻止提出新问题，因此请更新此答案：

$link    = mysqli_connect($host,$dbusername,$dbpassword,$dbname) or die("Error " . mysqli_error($link)); 
$query   = "SELECT * FROM student_information where student_id='{$_SESSION['user_id']}'";
$knowhow = mysqli_query($link, $query);

$data    = mysqli_fetch_array($result);     
$numRows = mysqli_num_rows($result); 

$i = 0;     
while($i < $numRows){
    echo $data[$i++] . "<br />";
}

// I would not use a while in this case. I would prefere a foreach
// just to prevent from using a endless loop and 1 row less code :)

foreach($data as $d){
    echo $d . "<br />";
}

请使用 MySqli 作为类，如 $db = new Mysqli();