Function Parameters and Return Values in PHP

Function parameters and return values enable PHP functions to accept inputs and output values. With this functionality, functions become flexible and reusable. Rather than coding rigid logic, programmers use functions to accept inputs and receive outputs.

What Are Function Parameters in PHP

Function parameters serve as placeholders for values. When calling a function, you use actual values referred to as arguments. PHP uses these values within the function.

Example

<?php
function greet($name) {
    echo "Hello " . $name;
}
greet("Varsha");
?>

In this example, $name is the parameter, and “Amit” is the argument.

Multiple Parameters in PHP Functions

Functions can take zero or more arguments. This alls the function to work on multiple values at once.

Example

<?php
function add($m, $n) {
    echo $m + $n;
}
add(22, 5);
?>

Default Parameter Values in PHP

PHP enables you to assign default values to parameters. Without an argument, the function uses the default value.

Example

<?php
function welcome($user = "Guest") {
    echo "Welcome " . $user;
}
welcome();
?>

What Is a Return Value in PHP

Return value allows the function to return a value from a function. So the function doesn’t print out ita values, it just returns a value that you can put in a variable or use again in your code.

Example

<?php
function square($num) {
    return $num * $num;
}
$result = square(8);
echo $result;
?>

Pass by Value in PHP Functions

PHP use pass-by-valued for passing arguments to function. In other words, the function gets a copy of the original value. Changes inside the function wouldn’t affect the argument.

Example

<?php
function increase($num) {
    $num = $num + 5;
}
$number = 10;
increase($number);
echo $number;
?>

The output remains 10 because PHP passes the value, not the variable itself.

Passing argument by Reference in PHP Functions

Passing variables by reference in PHP is done by using the ampersand (&). In this case the original variable is directly tampered with by the function.

Example

<?php
function increaseValue(&$num) {
    $num = $num + 5;
}
$number = 10;
increaseValue($number);
echo $number;
?>

Notice that the output is now 15 because the function modified the original variable.

Type Declarations in PHP Functions

In PHP You can specify type for function arguments and return value: In this cases, types help to avoid mistakes and keep code readable.

Example

<?php
function add(int $a, int $b): int {
    return $a + $b;
}
echo add(4, 6);
?>

Nullable Parameters and Return Types

PHP enables the use of nullable types by adding a question mark. In this scenario, the parameter or return type can be null.

Example

<?php
function getUsername(?string $name): ?string {
    return $name;
}
?>

Using Return Values in Conditions

Return values are what programmers rely on to handle the flow of control in their programs.

Example

<?php
function isAdult($age) {
    return $age >= 18;
}

if (isAdult(20)) {
    echo "Access granted";
}
?>

Useing Parameters and Return Values

Use arguments when the function takes input data. Return values to send data out of a function. In that situation, they make it possible to define reusable and composable functions.

Real World Example

In a form validation scenario, the input parameter to a function is the user’s input. Is the fact that, once this function process an input, it returns True or False. In this case, the function still keeps nice and reusable validation logic.

Returning Multiple Values in PHP

(PHP does not allow multiple return values.) But one through which programmers could get an array back to return more than one value.

Example

<?php
function calculate($a, $b) {
    return [$a + $b, $a * $b];
}
$data = calculate(4, 5);
echo $data[0];
?>

Parameters vs Return Values

Parameters are used to pass data into a function. Return values are used to pass data out of a function. Both parameters and return values increase the power of functions.

Conclusion

Function parameters and return values are useful for PHP programmers to write flexible and clean code. They enable programmers to use functions with different inputs and obtain useful results. After grasping these two concepts, it becomes easy to write complex PHP logic.

PHP Functions Introduction
PHP Variables and Data Types
PHP Control Structures