是否有必要使用全局变量？

Question

I am facing an issue regarding global variable scope in php. Below is my code snippet, can you tell me what am I doing wrong, and if the use of a global variable is unnecessary?

PHP version is 5.3.5

a.php

global $login;
$login = 0 ;
if(1==1) // here is some session checking condition
{
    echo "<BR/>inside if".__FILE__;
    $login = 1 ;
}

function alpha() {
    echo "<BR/>".__FUNCTION__;
    global $login;
    if($login)
    {
        echo "<br/>Login is available";
    }
    else
    {
        echo  "<br/>Login not available";
    }
}

b.php

$login=0;
if(1==1) // same condition define in a.php
{
    ECHO "<BR/>inside if".__FILE__;
    $login = 1;
}
if($login == 0)
{
    echo "out";
}

login.php

require_once("a.php");
require_once("b.php");
alpha();
echo "<BR/>".__FILE__;
echo $login;

It seems that my approach is wrong, what's a better method? Is declaring any variable global is necessary in this scenario? Will $login in b.php affect any variable?

note: if condition in both a.php and b.php is same, but i can not combine.

Answer 1

Use functions or class based approach.

A simple function would be

function is_logged_in() {
    static $login;
    if (isset($login)) return $login;
    $login = 0;
    if (1 == 1) { // here is some session checking condition
        $login = 1 ;
    }
    return $login;
}