PHP Fatal error: Constant expression contains invalid operations

Question

这是致命错误：

Fatal error: Constant expression contains invalid operations

我在这段代码中遇到致命错误：

<?php

class InfoClass {

    private $user_agent = $_SERVER['HTTP_USER_AGENT']; // error is on this line

    public static function getOS() { 

        global $user_agent;

        $os_platform = "Unknown OS Platform";

        ...
}

我正在使用php 7. 为什么会出现这个错误？谢谢

Answer 1

改为这样做

<?php

class InfoClass {
    private $user_agent;
    public function __construct(){
        $this->user_agent = $_SERVER['HTTP_USER_AGENT']; // error is on this line
    }

    public static function getOS() { 

    global $user_agent;

    $os_platform = "Unknown OS Platform";

    ...
}

希望对您有所帮助

PHP Fatal error: Constant expression contains invalid operations

PHP Fatal error: Constant expression contains invalid operations

php

error-handling

class

function

fatal-error