我应该把我的$ mysqli变量传递给每个函数？ [英] Should I pass my $mysqli variable to each function?

问题描述

我有一个问题从mysql_ *传递到mysqli面向对象。

我的 index.php 文件的结构，文件：

  include（'connect.php'）; 
 include（'function.php'）; 
  

connect.php文件包含：

 <？php 
 $ mysqli = new mysqli（localhost，root，test，test）; 
 
 if（mysqli_connect_errno（$ mysqli））{
 printf（Connection failed：％s\\\
，mysqli_connect_error（））; 
 exit（）; 
} 
？> 
  

在 function.php 文件中有一个函数 $ mysqli 连接，以

p $ p> $ result = $ mysqli - > query（SELECT * FROM $ table ORDER BY ID DESC）; // Seleziono tutto il contenuto della tabella


我无法管理它<函数$ mysqli变量，但是这不是必要的，当我使用mysql_ *不推荐使用的函数！

我能理解为什么，这个？

解决方案

用户定义的函数在PHP中有自己的变量范围。您需要将 $ mysqli 传递给函数作为参数，或者使用 global $ mysqli 启动函数。 p>

这个确切的问题是作为一个例子给出的 Variable scope page：

但是，在用户定义函数中，局部函数范围是
介绍。在函数内使用的任何变量默认为
，局限于局部函数作用域。 例如，此脚本不会
产生任何输出，因为echo语句引用$ a变量的本地
版本，并且它在此之前未分配值
您可能会注意到，这与C语言中的
有点不同，因为C中的全局变量自动
可用于函数，除非被本地
定义特别覆盖。这可能导致一些问题，人们可能会
无意中更改一个全局变量。在PHP全局变量中，
必须在函数中声明为全局变量，如果它们将在
函数中使用。

 <？php 
 $ a = 1; / *全局范围* / 
 
 function test（）
 {
 echo $ a; / *引用局部范围变量* / 
} 
 
 test（）; 
？> 
  

I am having a little problem passing from mysql_* to mysqli object oriented.

My index.php file is structured like including two files:

include('connect.php');
include('function.php');

The connect.php file contains:

<?php
$mysqli = new mysqli("localhost", "root", "test", "test");

if (mysqli_connect_errno($mysqli)) {
    printf("Connection failed: %s\n", mysqli_connect_error());
    exit();
}
?>

In the function.php file there is a function called showPage that takes no arguments but uses the $mysqli connection, in lines like...

$result = $mysqli -> query("SELECT * FROM $table ORDER BY ID DESC"); // Seleziono tutto il contenuto della tabella

I cannot manage it to work without passing to the function the $mysqli variable, but this was not necessary when I used mysql_* deprecated functions!

Can I understand why, and what's the best way to resolve this?

解决方案

User-defined functions have their own variable scope in PHP. You need to pass $mysqli to the function as a parameter, or start the function with global $mysqli.

This exact problem is given as an example on the Variable scope page:

However, within user-defined functions a local function scope is introduced. Any variable used inside a function is by default limited to the local function scope. For example, this script will not produce any output because the echo statement refers to a local version of the $a variable, and it has not been assigned a value within this scope. You may notice that this is a little bit different from the C language in that global variables in C are automatically available to functions unless specifically overridden by a local definition. This can cause some problems in that people may inadvertently change a global variable. In PHP global variables must be declared global inside a function if they are going to be used in that function.

<?php
$a = 1; /* global scope */ 

function test()
{ 
    echo $a; /* reference to local scope variable */ 
} 

test();
?>

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