访问构造函数私有专有 php

Question

我有这个代码：

class Person { 
     private $_firstName; 
     private $_lastName; 
     private $_age; 

     public function __construct($firstName, $lastName, $age) 
     { 
    echo 'Welcome '.$this->_firstName. ' '. $this->_lastName. 'that have '.''.$this->_age.'<br />';

     }

}
$obiect = new Person("dan", "Marian", 30);

为什么不显示有 30 个的 Welcome dan marian？

Answer 1

因为您没有为成员设置值：

public function __construct($firstName, $lastName, $age) 
{
    $this->_firstName = $firstName;
    $this->_lastName = $lastName;
    $this->_age = $age;

    echo …
}

Answer 2

这是因为您试图在初始化之前访问该值，您应该试试这个

public function __construct($firstName, $lastName, $age) 
 { 
     $this->_firstName=$firstName;
     $this->_lastName=$lastName;
     $this->_age=$age;

echo 'Welcome '.$this->_firstName. ' '. $this->_lastName. 'that have '.''.$this->_age.'<br />';

 }

访问构造函数私有专有 php

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