调用非对象 PHP 帮助上的成员函数 prepare() [英] Call to a member function prepare() on a non-object PHP Help
问题描述
我正在尝试编写一个 PHP 函数.这很简单.这只是一个查询数据库的准备好的语句，但我无法让它工作.我不断收到错误 Call to a member function prepare() 在非对象上.这是代码:
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();
每当我调用该函数时，我都会收到该错误.有人可以帮忙吗?
Any time I call the function i get that error. Can someone please help?
推荐答案
这是一个范围错误.您正在使 $DBH 成为一个全局变量.所以当你进入函数时，全局变量是不可用的.您有 5 种实际选择.
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.使用全局关键字
function doSomething() {
global $DBH;
//...
这不是一个好主意，因为它使维护和测试成为 PITA.想象一下尝试调试该函数调用.您现在需要找出 $DBH 的定义位置，以尝试弄清楚发生了什么......
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.将 $DBH 作为函数的参数
2. Make $DBH a parameter to the function
function doSomething(MySQLi $DBH) {
它的优点是明确.但这仍然不是很好，因为调用代码需要跟踪全局变量.
It has the advantage of being explicit. But it's still not great since the calling code then needs to keep track of the global variable.
3.创建一个函数来获取"$DBH 对象
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() {
$DBH = getDBH();
}
这样做的好处是完全解决了全局变量问题.但是也很难有多个连接或将任何代码重用于其他连接.
This has the advantage of getting around the global variable problem completely. But it's also hard to have multiple connections or re-use any of the code for other connections.
4.创建一个类来包装数据库访问
class Database {
public function __construct($host, $user, $pass) {
$this->DBH = new MySQli($host, $user, $pass);
}
public function doSOmething() {
$this->DBH->foo();
}
}
这为您封装了所有内容.所有数据库访问都将通过一个类进行，因此您无需担心全局变量访问或其他任何事情.
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.使用预先构建的类/框架
这是最好的选择，因为您无需担心自己动手.
This is the best option, since you don't need to worry about doing it yourself.
数据库访问类:
- 快速谷歌搜索以帮助您入门
- Doctrine ORM - 具有完整 ORM(对象映射)的完整数据库访问库
- ADODB - 一个与数据库无关的数据库访问库
- Pear MDB2 - 另一个数据库访问库
- 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:
真的，选择是无穷无尽的.找到你喜欢的东西，并坚持下去.它真的会让你的生活更轻松......
Really, the choices are endless. Find something you like, and stick with it. It really will make your life easier...
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