What are the types of functions in PHP?

Overview

A function is a piece of code used to perform a specific operation or task. It provides better reuse-ability and modularity for the application.

In PHP, it receives the input from the user in the form of arguments and performs particular actions. In some situations, it delivers the output in the form of a return value.

Types of functions in PHP

There are three types of functions in PHP:

  1. Named functions
  2. Anonymous functions
  3. Class methods

Named functions

Named functions are similar to any function given in any other language, except these have some syntactic differences. See an example of the Sum() function below.

<?php 
function Sum (int $num1, int $num2):int
{
  return $num1+$num2;
}
echo Sum(5,4)
?>

Explanation

  • Line 2: We define a Sum() function with two parameters of integer types ＄num1 and ＄num2, and return type int.
  • Line 4: We return the sum of the provided integers.
  • Line 5: We display the sum of two integers, 5 and 4, returned by the Sum()function.

Anonymous functions

Sometimes we need functions for one-time use. For this purpose, anonymous functions are defined without a user-given name and are known as lambda or closure functions. Generally, they are used to create an inline callback function.

Syntax

Let’s have a look at the given syntax of an anonymous function.

$var=function ($arg1, $arg2) { return $val; };

Example

Let’s look at the example code to write an anonymous function.

<?php
$Sum = function ($num1,$num2) {return $num1+$num2;};
echo "Sum of 3 and 7 is: " . $Sum(3,7);
?>

Explanation

  • Line 2: We define a function with two parameters of integer types ＄num1 and ＄num2, and return the sum of the provided integers.
  • Line 3: We display the sum of two integers returned by the anonymous function.

Class methods

A class method is a function encapsulated within the scope of a class.

Example

Let’s look at an example of the Sum() method in the Complex class.

<?php
class Complex
{
  private $real;
  private $img;
  public function __construct(float $real, float $img)
  {
    $this->real=$real;
    $this->img=$img;
  }
  public function Sum(Complex $c2):Complex
  {
    return new Complex($this->real+$c2->real, $this->img+$c2->img);
  }
}
$first = new Complex(2,4); 
$second = new Complex(3,5);
$sum = $first->Sum($second);
var_dump($sum);
?>

Explanation

  • Lines 4–5: We define the data-members ＄real and ＄img of the Complex class.
  • Lines 6–10: We define a constructor of the Complex class.
  • Lines 11–14: We define a Sum() method that returns the sum of two Complex class objects in a third object.
  • Lines 16–17: We create the instances of the Complex class.
  • Line 18: We call the Sum() method of the Complex class.
  • Line 19: We print the detail of the return value on screen.

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