問題描述

我在從 mysql_* 傳遞到面向?qū)ο蟮?mysqli 時遇到了一個小問題.

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

我的 index.php 文件的結(jié)構(gòu)就像包含兩個文件:

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

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

connect.php 文件包含:

The connect.php file contains:

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

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

在 function.php 文件中有一個名為 showPage 的函數(shù)，它不接受任何參數(shù)，但使用 $mysqli強> 連接，如...

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

如果不將 $mysqli 變量傳遞給函數(shù)，我就無法使其正常工作，但是當我使用 mysql_* 不推薦使用的函數(shù)時，這不是必需的！

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!

我能理解為什么嗎?解決這個問題的最佳方法是什么?

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

推薦答案

用戶定義的函數(shù)在 PHP 中有自己的變量作用域.需要將$mysqli作為參數(shù)傳遞給函數(shù)，或者用global $mysqli啟動函數(shù).

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.

這個確切的問題作為變量作用域的一個例子給出頁面:

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

然而，在用戶定義的函數(shù)中，局部函數(shù)作用域是介紹.默認情況下，函數(shù)內(nèi)部使用的任何變量都是僅限于局部函數(shù)范圍.比如這個腳本不會產(chǎn)生任何輸出，因為 echo 語句指的是本地$a 變量的版本，它沒有被賦值在這個范圍內(nèi).你可能會注意到這有點不同來自 C 語言，因為 C 中的全局變量是自動的可用于函數(shù)，除非被本地特別覆蓋定義.這可能會導(dǎo)致一些問題，因為人們可能無意中更改了全局變量.PHP中的全局變量必須如果要在函數(shù)中使用，則在函數(shù)中聲明為全局那個功能.

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();
?>

這篇關(guān)于我應(yīng)該將 $mysqli 變量傳遞給每個函數(shù)嗎?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！