为什么我会出现致命错误:不在对象上下文中使用$this - Why am I getting the Fatal error: Using $this when not in object context?

Why am I getting the Fatal error: Using $this when not in object context?

我正在尝试制作一个动态菜单，但我一直收到致命的错误。这是代码：

class Menu {
public $menu;
function __contstruct() {
    $this -> menu = array("Home" => "index.php",
    //"Eat" => array("Casual" => "casual.php", "Fine dining" => "fine_dining.php"),
    "Contact" => "contact.php");
}
public static function page_name() {
    return substr($_SERVER["SCRIPT_NAME"], strrpos($_SERVER["SCRIPT_NAME"], "/") + 1);
}
public static function menu_list() {
    $menu_list = "";
    foreach ($this->menu as $name => $url) {
        echo "<li ";
        if ($url == $this -> pagename()) {
            $menu_list .= "class='active'";
        }
        $menu_list .= "><a href='";
        $menu_list .= $url;
        $menu_list .= "'>" . $name . "</a></li>";
        return ($menu_list);
    }
}
}
?>

并用调用它

$nav = new Menu();
echo $nav->menu_list();

请帮我弄清楚为什么它不起作用。

不能在静态方法中使用$this。$this用于对象。当您没有实例时，使用self引用方法所包含的类。

如果要在对象上下文中使用，请从方法签名中删除static。

更重要的是，您拼写的"construct"不正确，键入的是"pagename"而不是"page_name"。这项工作：

<?php
class Menu {
public $menu;
function __construct() {
    $this -> menu = array("Home" => "index.php",
    //"Eat" => array("Casual" => "casual.php", "Fine dining" => "fine_dining.php"),
    "Contact" => "contact.php");
}
public function page_name() {
    return substr($_SERVER["SCRIPT_NAME"], strrpos($_SERVER["SCRIPT_NAME"], "/") + 1);
}
public function menu_list() {
    $menu_list = "";
    foreach ($this->menu as $name => $url) {
        echo "<li ";
        if ($url == $this -> page_name()) {
            $menu_list .= "class='active'";
        }
        $menu_list .= "><a href='";
        $menu_list .= $url;
        $menu_list .= "'>" . $name . "</a></li>";
        return ($menu_list);
    }
}
}
$nav = new Menu();
echo $nav->menu_list();