How to call PHP functions?

There are four ways to call functions in PHP: regular calls, parameter passing, return values ​​and variable functions. Regular calls use function names and parameters; parameter passing can be by value or by reference; return values ​​use the return keyword; variable functions use the variable name as the function name.

How to call PHP functions

In PHP, functions can be called in the following four ways:

1. Conventional call

The most basic function calling method is:

function_name(arg1, arg2, ...);

For example:

echo hello(); // 输出："Hello"

2. Parameter passing

Function parameters can be passed by value or by reference:

• Value transfer: Pass the value of the variable to the function. Modifications to the variable within the function will not affect variables outside the function.
• Pass by reference: Pass the reference of the variable to the function. Modifications to the variable within the function will affect variables outside the function.

Pass by reference by adding & symbols in front of the parameter name, for example:

function swap(&$a, &$b) {
    $temp = $a;
    $a = $b;
    $b = $temp;
}

$a = 1;
$b = 2;
swap($a, $b);
echo "$a, $b"; // 输出："2, 1"

3. Return value

The function can return A value, use the return keyword, for example:

function double(int $num): int {
    return $num * 2;
}

echo double(5); // 输出："10"

4. Variable function

The variable function is a special function calling method in PHP, which allows the variable name to be used as a function name. The syntax is as follows:

$function_name($arg1, $arg2, ...);

For example:

<?php
$hello = "Hello";
$hello("World!"); // 等同于 echo "Hello World!";
?>

Practical case

Example: Calculate the average of two numbers

<?php
function average(int $num1, int $num2): float {
    return ($num1 + $num2) / 2;
}

// 调用函数
echo "两数的平均值为：" . average(5, 10) . "\n"; // 输出："7.5"
?>

Passed With the function calling method introduced above, we can flexibly use PHP functions to complete various programming tasks.

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