php - 为什么下面的代码打印出 10 而不是 null？

Question

以下代码输出10。这是为什么？

<?php 

class a{
    var $c;

    public function a(){
        $this->c=10;
    }
}

class b extends a{

    public function print_a(){
        print $this->c;
    }
}

$b=new b;
$b->print_a();

Answer 1

因为 public function a() 是一个构造函数。

For backwards compatibility, if PHP 5 cannot find a __construct() function for a given class, and the class did not inherit one from a parent class, it will search for the old-style constructor function, by the name of the class.

查看更多信息 PHP constructor manual