PHP函数如何实现函数指针？

call_user_func($callback, ...$params);

<?php

// 定义 calculate 函数
function calculate($num1, $num2, $operation)
{
    switch ($operation) {
        case '+':
            return $num1 + $num2;
        case '-':
            return $num1 - $num2;
        case '*':
            return $num1 * $num2;
        case '/':
            return $num1 / $num2;
        default:
            throw new InvalidArgumentException('Invalid operation.');
    }
}

// 定义 perform_operation 函数
function perform_operation($num1, $num2, $operation)
{
    // 使用 call_user_func 调用 calculate 函数
    return call_user_func('calculate', $num1, $num2, $operation);
}

// 获取用户输入
$num1 = readline('Enter the first number: ');
$num2 = readline('Enter the second number: ');
$operation = readline('Enter the operation (+, -, *, /): ');

// 调用 perform_operation 函数
$result = perform_operation($num1, $num2, $operation);

// 输出结果
echo "The result is: $result";
?>