What are the elements of a PHP function?

PHP functions include 4 elements: function declaration, parameter list, function body and return value. A function declaration begins with function, specifying the function name and optional parameter list. The parameter list contains the variables accepted by the function. The function body contains the code of the function and is defined within curly braces. The return value specifies the type of value returned by the function or means that no value is returned.

Detailed explanation of PHP function elements

PHP function is a block that defines a set of instructions that can be reused by other parts of the code . A PHP function consists of the following elements:

1. Function declaration

The function declaration starts with the keyword function, followed by the function name and parentheses. Parentheses can contain the parameter list of the function.

function myFunction($parameter1, $parameter2) {
  // 函数体
}

2. Parameter list

The parameter list of a function contains the variables accepted by the function. Parameters can be value types or reference types. Value types are passed by value, while reference types are passed by reference.

function myFunction(int $valueType, &int $refType) {
  // 函数体
}

3. Function body

The function body contains the code of the function. It is defined within curly braces and can contain statements, expressions, and function calls.

function myFunction() {
  echo "Hello, world!";
}

4. Return value

The function can return a value. The type of the return value must match the type specified in the function declaration. You can also use the void key to indicate that the function does not return any value.

function myFunction(): int {
  return 10;
}

Practical case

The following is an example of a PHP function that calculates the circumference of a circle:

function circumference($radius) {
  return 2 * pi() * $radius;
}

$radius = 5;
$circumference = circumference($radius);

echo "圆周长为：$circumference";

This function receives the radius as a parameter and returns the circumference of the circle . In practice, we pass in a radius of 5 and print the result.

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