小弟我有有关问题

我有问题求助
刚接触PHP ,写了如下的一小段，$x->name();为什么打印出来是空啊？

PHP code

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interface man{
    function talk();
}
abstract class person{
    abstract function name();
    abstract function age();
    var $c="这是一个抽象类<br>";
}
class xiaoming extends person implements man {
    function name(){
        echo ("xiaoming<br>");
    }
    function age(){
        echo ("12"."<br>");
    }
    function talk(){
        echo ("love<br>");
    }
}
class xiaoli extends person implements man{
    var $mingzi;
    function _construct($mingzi){
        $this->mingzi=$mingzi;
    }
    function name(){
        echo ($this->mingzi."<br>");
    }
    function age(){
        echo ("13<br>");
    }
    function talk(){
        echo ("you");
    }
}
$p = new xiaoming();

$p->name();
$p->age();
$p->talk();

$x = new xiaoli("xiaoli");
$x->age();
$x->name();
$x->talk();

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