Creation and management of PHP user-defined functions

PHP User-defined functions can perform specific tasks and be used repeatedly. Creating a custom function requires using a specific syntax to specify the function name and parameters. Example shows how to calculate the area of ​​different shapes. Calling a custom function is similar to calling a built-in function. Managing custom functions includes registering, deleting, and viewing created functions.

Create and manage PHP user-defined functions

What are user-defined functions?

User-defined functions are blocks of code that you can create for yourself to perform specific tasks and reuse them as needed.

Create a custom function

To create a custom function, use the following syntax:

function function_name($parameter1, $parameter2, ...) {
    // 函数的代码
}

• function_name is the name of the function.
• parameter1, parameter2 are optional parameters if you want the function to receive input.

Example practice: Calculate area

Suppose you need to calculate the area of ​​different shapes, you can use the following custom function:

function calcArea($shape, $parameters) {
    switch ($shape) {
        case "rectangle":
            return $parameters["length"] * $parameters["width"];
        break;
        case "circle":
            return pi() * $parameters["radius"] ** 2;
        break;
        default:
            return "Invalid shape.";
    }
}

$rectArea = calcArea("rectangle", ["length" => 5, "width" => 3]);
$circleArea = calcArea("circle", ["radius" => 2]);

echo "Area of rectangle: $rectArea";
echo "<br>";
echo "Area of circle: $circleArea";

Calling a custom function

Calling a custom function is similar to calling a built-in function:

function_name($argument1, $argument2, ...);

• argument1, argument2 is the actual value passed to the function.

Manage custom functions

• Register function: Before using it, you need to use register_shutdown_function() function to register a custom function.
• Delete function: To delete a custom function, use the unregister_shutdown_function() function.
• View functions: By using the get_defined_functions() function you can get a list of all custom functions that have been created.

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