为什么需要访问权限?
防止覆盖变量名称和函数名称
我们下来看一下public的使用,public是可以从任何地方访问的最广泛的访问限定符。
假设A先生开发overlapFuncBase,B先生继承overlapFuncBase创建了overlapFunc的例子。
<?php
class overlapFuncBase {
public $s = 1;
}
class overlapFunc extends overlapFuncBase {
public $s = 2;
}
$obj_overlap = new overlapFunc();
var_dump($obj_overlap);
结果
object(overlapFunc)#1 (1) {
["s":"overlapFunc":public] => int(2)
}
在B overlapFunc中,我可以使用由A先生创建的overlapFuncBase,但由于变量名$ s是相同的,覆盖了它。
所以这时就需要访问修饰符。
<?php
class overlapFuncBase {
private $s = 1;
}
class overlapFunc extends overlapFuncBase {
private $s = 2;
}
$obj_overlap = new overlapFunc();
var_dump($obj_overlap)
结果
object(overlapFunc)#1 (2) {
["s":"overlapFunc":private] => int(2)
["s":"overlapFuncBase":private] => int(1)
}
与第一个代码的不同之处在于我们在变量$ s之前将访问修饰符public更改为private。
private表示你只能在自己的类中访问。
因此,即使是A创建的每个类都有相同变量名,现在也可以获得不同的结果。
访问修饰符的类型
访问修饰符有private、protected和public
对应范围按以下顺序增加
private → protected → public
还有另一个名为static的特殊访问修饰符,如果你指定了类名,你可以在任何地方使用它。