Question

我正在编写一个PHP应用程序，我正在尝试一个奇怪的bug。我有一个名为权限的类，表示为：

//Permissions class
class Permission {
    //Permission name
    protected $permission_name = "";

    //Constructor method
    function __construct($name) {
        //Get global reference for variables used here
        global $permission_name;

        //Save the permission name
        $permission_name = $name;

        echo("<br>" . $name . "<br>");
    }

    //Compare permissions
    function compare($permission) {
        //Get global reference for variables used here
        global $permission_name;

        //Break down the permissions into arrays
        $permission_a_data = explode(".", $permission_name);
        $permission_b_data = explode(".", $permission);

        //Iterate through the permission values
        foreach($permission_a_data as $index=>$perm) {
            //Check for a wildcard permission
            if($perm == "*") {
                //User has wildcard permission
                return true;
            }
            //Check if permission has ended
            if(!isSet($permission_b_data[$index])) {
                //User does not have adequate permission
                return false;
            }
            //Check if permission is different
            if($permission_b_data[$index] != $perm) {
                //Permissions differ
                return false;
            }
        }

        //If application reaches this point, permissions are identical
        return true;
    }

    //Get the name
    function get_name() {
        //Get global reference for objects used here
        global $permission_name;
        //Return the name
        return $permission_name;
    }
}

我在应用程序的其他地方有一些代码，如：

$permission1 = new Permission("This.is.a.test");
$permission2 = new Permission("test.a.is.This");
echo("<br>DEBUG:<br>");
echo($permission1->get_name() . "<br>");
echo($permission2->get_name() . "<br>");

然而第二段代码总是打印出来：

DEBUG:
test.a.is.This
test.a.is.This

我不知道为什么会这样，并且非常感谢任何帮助。

Answer 1

每次拨打$permission_name个实例时都会覆盖new，因为function __construct $permission_name内global为->get_name()，global返回相同的{{1}}变量。

Answer 2

从班级中删除global $permission_name行。

您可以使用$this来引用该班级的当前实例。因此，您可以使用$this->permission_name访问当前instance.some的$permission_name，例如，

class Permission {
    //Permission name
    protected $permission_name = "";

    //Constructor method
    function __construct($name) {

        $this->permission_name = $name;

    }

    function compare($permission) {

        //Break down the permissions into arrays
        $permission_a_data = explode(".", $this->permission_name);

        //....
    }

    function get_name() {

        //Return the name
        return $this->permission_name;
   }

}

无法创建类的多个实例

2 个答案: