在PHP中拥有$ this和self ::有什么意义? [英] What is the point of having $this and self:: in PHP?

问题描述

为什么PHP要求您显式编写$this?我会理解您是否必须在此处使用$this

Why does PHP require you to explicitly write $this? I would understand if you had to use $this here:

function foo($bar) {
   $this->bar = $bar;
}

但是您必须使用如下所示的冗长代码显式地编写它:

But you must write it explicitly in verbose code that looks like this:

$this->var3 = globalFun($this->var, $this->var2[$this->anotherVar], $this->method());

相对于:

$var3 = globaFun($var, $var2[$anotherVar], method());

那么$this的意义是什么?

为什么我们必须区分静态引用和实例?我们为什么需要:

Why do we have to differentiate static references and instances? Why do we need:

static function getValue() {
   return self::value;
}

如果有问题的变量/方法是静态的，PHP是否无法在运行时查找?现在，如果我想将方法​​从静态更改为非静态，则必须将所有self::替换为$this->(反之亦然).

Can't PHP find out at runtime if the variable/method in question is static? Now if I want to change a method from static to non-static, I have to replace all those self:: with $this-> (and vice-versa).

如果我们的$this表现得像Java一样好吗?

Wouldn't it be better if we had a $this that behaves like it does in Java?

推荐答案

好的，让我们无需在任何地方编写$this.看一下这种情况:

Okay, so let's remove the need for writing $this everywhere. Take a look at this situation:

class Foo {
    public function setBar($value) {
        $bar = $value;
    }
}
$foo = new Foo();
$foo->setBar('some value');

$bar是局部变量还是$foo的成员?

Is $bar a local variable or a member of $foo?

必须有所区别.他们本可以允许使用var关键字声明局部变量，但是这并不能向后兼容，而且对于从旧版本的PHP升级的人们会造成极大的困扰.

There has to be some differentiation. They could have allowed declaration of local variables with the var keyword, but that would not have been backwards-compatible and would have been very confusing to people upgrading from older versions of PHP.

self::同样适用.解释器如何知道您要调用的函数是全局的还是特定于该类的?

Same thing applies to self::. How does the interpreter know whether the function you wanted to call is global or specific to the class?

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