PHP Functions

In this article, we will cover the following topics:

Introduction of PHP Functions

PHP functions are a piece of code that can be reused.

Advantages of PHP functions:

Code Reusability.
Reducing code duplication.
Break a larger number of codes into small pieces.

PHP functions are divided into two sections such as Built-in function and user-defined function. Built-in functions are part of the language of PHP. User-Defined function, that can be created by a programmer according to needs. The user-Defined function executes by the call of the function.

Declaring Functions:

A PHP function declares by keyword function.

Syntax:

 <?php function userDefineFunctionName() { //Block of Code } ?>

<?php

function userDefineFunctionName() {

//Block of Code

}

In the above syntax,

Start a keyword function for creating a function.
Put the name of function example: userDefineFunctionName.
Start a curly( { ) brace.
Write a block of code.
Close curly( } ) brace.

Example:

 <?php function add() { echo 10 + 7; } add();//Output: 17 ?>

<?php

function add() {

echo 10 + 7;

}

add();//Output: 17

In the above example, define a function “add” and it is adding two values (10 + 7). After declaration, it will show 17 as an output. If you do not declare the function then it will not show anything.

Passing Arguments to Functions:

PHP function allows passing arguments to the function. You can pass multiple arguments according to requirements.

 <?php function operations($a, $b) { echo $a + $b; } operations(10,5);//Output: 15 ?>

<?php

function operations($a, $b) {

echo $a + $b;

}

operations(10,5);//Output: 15

Let’s take an example using a switch case:

 <?php function operations($a, $b, $operator) { switch($operator) { case '+': echo $a + $b; break; case '-': echo $a - $b; break; case '*': echo $a * $b; break; case '/': echo $a / $b; break; case '%': echo $a % $b; break; default: echo "Enter correct operator."; break; } } operations(12,18,'+');//Output: 30 operations(20,15,'-');//Output: 5 operations(12,3,'*');//Output: 36 operations(15,5,'/');//Output: 3 operations(16,3,'%');//Output: 1 ?>

<?php

function operations($a, $b, $operator) {

switch($operator) {

case '+':

echo $a + $b;

break;

case '-':

echo $a - $b;

break;

case '*':

echo $a * $b;

break;

case '/':

echo $a / $b;

break;

case '%':

echo $a % $b;

break;

default:

echo "Enter correct operator.";

break;

}

operations(12,18,'+');//Output: 30

operations(20,15,'-');//Output: 5

operations(12,3,'*');//Output: 36

operations(15,5,'/');//Output: 3

operations(16,3,'%');//Output: 1

PHP Variables Scope:

PHP variable scope is a part of a program that can be accessed or visible.

There are three types of Variable scope:

Local Scope
Global Scope

Local and Global Scope:

A variable declares inside the function is called Local Scope that accesses only inside the function.

Example:

 <?php function checkLocalScope() { $var = 5; //Local Scope echo $var; } checkLocalScope(); echo $var;//It will show error: "PHP Notice: Undefined variable" ?>

<?php

function checkLocalScope() {

$var = 5; //Local Scope

echo $var;

}

checkLocalScope();

echo $var;//It will show error: "PHP Notice: Undefined variable"

A variable declares outside the function is called Global Scope that can be accessed inside the function by global keyword.

 <?php $x = 5; function checkGlobalScope() { global $x; echo $x; } checkGlobalScope(); echo $x; ?>

<?php

$x = 5;

function checkGlobalScope() {

global $x;

echo $x;

}

checkGlobalScope();

echo $x;

PHP Global scope variable also accesses by $GLOBALS array. It associates with the key of the name of the variable.

 <?php $x = 5; function globalVariable() { echo $GLOBALS['x']; } globalVariable(); ?>

<?php

$x = 5;

function globalVariable() {

echo $GLOBALS['x'];

}

globalVariable();

Returning Values from a Function

You can return value, array, or object by return keyword in the function and the return stops the execution of the function.

Example:

 <?php function add($a, $b) { $c = $a + $b; return $c; } $a= 10; $b = 15; $sum = add($a, $b);//Assign the return value after calling the function to $sum variable. echo "The Sum of $a and $b: ".$sum; ?>

<?php

function add($a, $b) {

$c = $a + $b;

return $c;

}

$a= 10;

$b = 15;

$sum = add($a, $b);//Assign the return value after calling the function to $sum variable.

echo "The Sum of $a and $b: ".$sum;

In the above example, the function is written for adding two numbers and returning the sum of two values($a, $b). Assigned the return value after calling the function to the $sum variable and it will show the following output:

Output:

 The Sum of 10 and 15: 25

1	The Sum of 10 and 15: 25

Recursive Function in PHP

A recursive function is a function that calls itself continually until the terminating state arrives.

Let’s take an example:

 <?php function mathTable($var, $i) { if($i <= 10) { echo $var * $i.","; mathTable($var, ++$i); } else { return false; } } mathTable(2, 1); ?>

<?php

function mathTable($var, $i) {

if($i <= 10) {

echo $var * $i.",";

mathTable($var, ++$i);

} else {

return false;

}

mathTable(2, 1);

In the above example, printing the table of 2 without using the PHP loop.

Output:

 2 4 6 8 10 12 14 16 18 20

1	2 4 6 8 10 12 14 16 18 20

Predefined Functions in PHP:

PHP has many pre-defined functions which are called built-in functions.

You can check those functions here: https://www.php.net/manual/en/indexes.functions.php

Introduction of PHP Functions

Declaring Functions:

Passing Arguments to Functions:

PHP Variables Scope:

Local and Global Scope:

Returning Values from a Function

Recursive Function in PHP

Predefined Functions in PHP:

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