如何将变量和/或函数从一个php文件传递到另一个php文件？

// file1.php
$variable = "Hello, World!";
function myFunction() {
    echo "This is a function.";
}

// file2.php
include 'file1.php';
echo $variable; // 输出：Hello, World!
myFunction(); // 输出：This is a function.

// file1.php
session_start();
$_SESSION['variable'] = "Hello, World!";

// file2.php
session_start();
echo $_SESSION['variable']; // 输出：Hello, World!

// file1.php
$variable = "Hello, World!";
echo "<a href='file2.php?data=$variable'>Go to file2</a>";

// file2.php
$variable = $_GET['data'];
echo $variable; // 输出：Hello, World!

// file1.php
$variable = "Hello, World!";
include 'file2.php';

// file2.php
function myFunction($data) {
    echo $data;
}
myFunction($variable); // 输出：Hello, World!