php 错误：不在对象上下文中使用 $this
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Error: Using $this when not in object context
提问by Leo Houer
I have looked for other questions covering this error, but could not find a case that applies to my problem.
我已经寻找了涵盖此错误的其他问题，但找不到适用于我的问题的案例。
Basically the static method in my class invokes a non-static method which in return invokes another non-static method.
基本上，我的类中的静态方法调用一个非静态方法，该方法反过来调用另一个非静态方法。
This throws an Fatal error:
这会引发致命错误：
Fatal error: Using $this when not in object context in class.php on line ...
致命错误：当不在 class.php 中的对象上下文中时使用 $this 在线...
I can't figure out why it is not okay to call a non-static class method from another non-static class method via $this. Is it because they are both invoked from a static function and hence there is no $this instance ?
我不明白为什么通过 $this 从另一个非静态类方法调用非静态类方法是不行的。是因为它们都是从静态函数调用的，因此没有 $this 实例吗？
Here is the (simplified) class:
这是（简化的）类：
class Redis_Provision {
public $redis = NULL;
public function redis_query()
{
if(is_null($this->redis)) {
$this->setBackend(); <------- This throws the fatal error
}
return $this->redis;
}
public function setBackend()
{
$this->redis = new Redis();
$this->redis->connect();
}
public static function activate()
{
if( self::redis_query()->ping())
{
// Do stuff
}
}
}
Which i would invoke via:
我将通过以下方式调用：
$redis_provision = new Redis_Provision();
$redis_provision->activate();
采纳答案by George Brighton
The error occurs because you've called a non-static method statically (this will have risen an E_STRICT- check your error reporting), which doesn't stop execution but means there's no object context ($thiscannot be used).
发生错误是因为您静态调用了一个非静态方法（这将引发E_STRICT- 检查您的错误报告），这不会停止执行，但意味着没有对象上下文（$this无法使用）。
The proper way to fix the error is to instantiate the class in activate(), and call the redis_query()method on the object, e.g.
修复错误的正确方法是在 中实例化类activate()，并调用redis_query()对象上的方法，例如
$redis_provision = new Redis_Provision();
if($redis_provision->redis_query()->ping()) { ... }
This means that redis_query()executes with a context, and so functions normally.
这意味着redis_query()使用上下文执行，因此正常运行。
Also, the activate()method is static, so you don't need to create a new object in your invocation code. You can just call Redis_Provision::activate()directly.
此外，该activate()方法是静态的，因此您无需在调用代码中创建新对象。Redis_Provision::activate()直接打电话就可以了。
