php 使用 mysqli 包含连接的正确方法
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The correct way to include connection using mysqli
提问by jaypabs
Below is my code under db.php
下面是我在 db.php 下的代码
<?php
$con = mysqli_connect('localhost', 'root', '', 'mydb');
/* check connection */
if (!$con) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
?>
Under index.php I include db.php and functions.php as:
在 index.php 下，我将 db.php 和 functions.php 包括为：
include("includes/db.php");
include("includes/functions.php");
functions.php is also using the db.php connection. I don't have problem before when using mysql. But after I change mysql to mysqli I got an error "Warning: mysqli_query() expects parameter 1 to be mysqli, null given in" in my functions.php.
functions.php 也使用 db.php 连接。以前用mysql没有问题。但是在我将 mysql 更改为 mysqli 后，我在我的functions.php 中收到一个错误“警告：mysqli_query() 期望参数 1 为 mysqli，给定为空”。
This is the function under functions.php that has an error:
这是functions.php下有错误的函数：
function get_type($r_id){
$result=mysqli_query($con, "select type from rooms where id=$r_id") or die("select type from rooms where id=$r_id"."<br/><br/>".mysqli_error());
$row=mysqli_fetch_assoc($result);
return $row['type'];
}
My solution is to add db.php in every function under functions.php that calls mysqli like:
我的解决方案是在functions.php下的每个调用mysqli的函数中添加db.php，例如：
function get_type($r_id){
include("includes/db.php");
$result=mysqli_query($con, "select type from rooms where id=$r_id") or die("select type from rooms where id=$r_id"."<br/><br/>".mysqli_error());
$row=mysqli_fetch_assoc($result);
return $row['type'];
}
I am wondering if this is the correct solution.
我想知道这是否是正确的解决方案。
回答by Dale
The problem is that $con is not available to your functions
问题是 $con 对您的功能不可用
You can add another argument to each function
您可以为每个函数添加另一个参数
function get_type($con, $r_id)...
and then pass $con into it
然后将 $con 传递给它
include('includes/db.php');
include('includes/functions.php');
$blah = get_type($con, 5);
OR
或者
You can make $con accessible to each function by adding this global $con;for example
例如，您可以通过添加它global $con;来使每个函数都可以访问 $con
function get_type($r_id){
global $con;
$result=mysqli_query($con, "select type from rooms where id=$r_id") or die("select type from rooms where id=$r_id"."<br/><br/>".mysqli_error());
$row=mysqli_fetch_assoc($result);
return $row['type'];
}
The choice my friend.. is yours
我的朋友的选择..是你的
(there may be other ways to skin this cat)
（可能还有其他方法可以给这只猫剥皮）
回答by Lucifer
set $conglobal in function:
$con在函数中设置全局：
function get_type($r_id){
global $con;
$result=mysqli_query($con, "select type from rooms where id=$r_id") or die("select type from rooms where id=$r_id"."<br/><br/>".mysqli_error());
$row=mysqli_fetch_assoc($result);
return $row['type'];
}
