What is the main purpose of using functions?

The primary purpose of functions is to break up complicated computations into meaningful chunks and name them. The functions may return a computed value to its caller (its return value), or provide various result values or output parameters.

Call a function:

To call the function, juts write its name followed by parentheses( ):

<?php

function_name( );

?>

Parameters vs Arguments:

Parameters are temporary variable names within functions.

The arguments can be thought of as the vale that is assigned to that temporary variable.

For example:

<?php

 function welcome_user($username)

{

  echo ‘Welcome’ . $username. ‘!’ ;

?>

In this example $username is a function parameter.

<?php

welcome_user(‘Admin’);

?>

In this function call, the literal string ’Admin’ is an argument.

Use return statement to return a value from a function.

Call By Reference:

In case of PHP call by reference, actual value is modified if it is modified inside the function. In such case, you need to use & (ampersand) symbol with formal arguments. The & represents reference of the variable.

<?php

// Function that modifies the value of a variable passed by reference

function increment(&$num) {

    $num++;

}

// Using call by reference

$value = 10;

echo "Before increment: $value <br>"; // Outputs: Before increment: 10

increment($value);

echo "After increment: $value"; // Outputs: After increment: 11

?>

In the ‘increment( )’ function, ‘$num’ is passed by reference with’&$num’. This means any changes mde to ‘$num’ inside the function will directly affect the original variable passed to it.

Without passing by reference, changes made to variables inside a function are confined to the function’s scope and do not affect the variables outside the function. However with call by reference, changes made insde the function affect the original variables.