問題描述

我正在嘗試編寫一個(gè) PHP 函數(shù).這很簡單.這只是一個(gè)查詢數(shù)據(jù)庫的準(zhǔn)備好的語句，但我無法讓它工作.我不斷收到錯(cuò)誤 Call to a member function prepare() 在非對(duì)象上.這是代碼:

I am trying to write a PHP function. It is very simple. It is just a prepared statement that queries the database, but I can not get this to work. I keep recieving the error Call to a member function prepare() on a non-object. here is the code:

$DBH = new mysqli("host", "test", "123456", "dbname");
function selectInfo($limit, $offset){
    $stmt = $DBH->prepare("SELECT * FROM information LIMIT ?,?");
    $stmt->bind_param("ii", $limit, $offset);
    $stmt->execute();
    }
selectInfo();

每當(dāng)我調(diào)用該函數(shù)時(shí)，我都會(huì)收到該錯(cuò)誤.有人可以幫忙嗎?

Any time I call the function i get that error. Can someone please help?

推薦答案

這是一個(gè)范圍錯(cuò)誤.您正在使 $DBH 成為一個(gè)全局變量.所以當(dāng)你進(jìn)入函數(shù)時(shí)，全局變量是不可用的.您有 5 種實(shí)??際選擇.

It's a scoping error. You're making $DBH a global variable. So when you enter the function, the global variable is not available. You have 5 real options.

1.使用全局關(guān)鍵字

function doSomething() {
    global $DBH;
    //...

這不是一個(gè)好主意，因?yàn)樗咕S護(hù)和測試成為 PITA.想象一下嘗試調(diào)試該函數(shù)調(diào)用.您現(xiàn)在需要找出 $DBH 的定義位置，以嘗試弄清楚發(fā)生了什么......

This is not a good idea, since it makes maintenance and testing a PITA. Imagine trying to debug that function call. You now need to go find out where $DBH is defined to try to figure out what's going on...

2.將 $DBH 作為函數(shù)的參數(shù)

2. Make $DBH a parameter to the function

function doSomething(MySQLi $DBH) {

它的優(yōu)點(diǎn)是明確.但這仍然不是很好，因?yàn)檎{(diào)用代碼需要跟蹤全局變量.

It has the advantage of being explicit. But it's still not great since the calling code then needs to keep track of the global variable.

3.創(chuàng)建一個(gè)函數(shù)來獲取"$DBH 對(duì)象

3. Create a function to "get" the $DBH object

function getDBH() {
    static $DBH = null;
    if (is_null($DBH)) {
        $DBH = new mysqli(...);
    }
    return $DBH;
}

function doSomething() {
    $DBH = getDBH();
}

這樣做的好處是完全解決了全局變量問題.但是也很難有多個(gè)連接或?qū)⑷魏未a重用于其他連接.

This has the advantage of getting around the global variable problem completely. But it's also hard to have multiple connections or re-use any of the code for other connections.

4.創(chuàng)建一個(gè)類來包裝數(shù)據(jù)庫訪問

class Database {
    public function __construct($host, $user, $pass) {
        $this->DBH = new MySQli($host, $user, $pass);
    }
    public function doSOmething() {
        $this->DBH->foo();
    }
}

這為您封裝了所有內(nèi)容.所有數(shù)據(jù)庫訪問都將通過一個(gè)類進(jìn)行，因此您無需擔(dān)心全局變量訪問或其他任何事情.

This encapsulates everything for you. All database access will go through a single class, so you don't need to worry about global variable access or anything else.

5.使用預(yù)先構(gòu)建的類/框架

這是最好的選擇，因?yàn)槟鸁o需擔(dān)心自己動(dòng)手.

This is the best option, since you don't need to worry about doing it yourself.

數(shù)據(jù)庫訪問類:

• 快速谷歌搜索以幫助您入門
• Doctrine ORM - 具有完整 ORM(對(duì)象映射)的完整數(shù)據(jù)庫訪問庫
• ADODB - 一個(gè)與數(shù)據(jù)庫無關(guān)的數(shù)據(jù)庫訪問庫
• Pear MDB2 - 另一個(gè)數(shù)據(jù)庫訪問庫

• A quick google search to get you started
• Doctrine ORM - A complete database access library with full ORM (Object Mapping)
• ADODB - A database agnostic database access library
• Pear MDB2 - Another database access library

完整框架:

• Zend 框架
• 鋰框架
• 代碼點(diǎn)火器
• (真的還有很多，我不打算再列出來了，因?yàn)槟鞘橇硪粋€(gè)問題……)

真的，選擇是無窮無盡的.找到你喜歡的東西，并堅(jiān)持下去.它真的會(huì)讓你的生活更輕松......

Really, the choices are endless. Find something you like, and stick with it. It really will make your life easier...

這篇關(guān)于調(diào)用非對(duì)象 PHP 幫助上的成員函數(shù) prepare()的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！