Programonic

Before you start

PHP basics.

Declare typed parameters and return values.
Predict the sample output and explain the state changes.
Complete the practice task and check the boundary cases.

The concept

A function is declared with function, and its parameters and return type can carry type declarations such as array and float. PHP then checks the values when the function runs.

array_sum adds the numbers in an array and count returns how many there are. The echo statement accepts several comma-separated values. A float that has no fractional part prints without a decimal point, so 86.0 is shown as 86.

Code example

PHP

<?php
function average(array $values): float {
    return array_sum($values) / count($values);
}

echo average([82, 91, 76, 95]), "\n";
echo round(average([1, 2]), 1), "\n";

Output

86
1.5

Example details

Follow the code

Open the walkthrough to inspect the example one step at a time.

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Guided walkthroughReady

1<?php

2function average(array $values): float {

3 return array_sum($values) / count($values);

4}

6echo average([82, 91, 76, 95]), "\n";

7echo round(average([1, 2]), 1), "\n";

Follow the example

Start to inspect the source, values, and output. These prepared steps explain the published sample; grouped loop steps describe multiple iterations.

View the complete dry-run table

Prepared trace of the published program. Some rows group repeated iterations.
What happens	State after step	Output so far
Accept an array and return a float.	`—`	—
344 / 4 is 86.0, echoed as 86.	`return = 86.0`	86
3 / 2 is 1.5; round keeps one decimal.	`return = 1.5`	86 1.5

Behind the scenes

How PHP processes this code

The PHP runtime executes the script. echo writes to the response or terminal output.

Cost and common mistakes

O(n) time and O(1) extra space.

Dividing by count([]) throws DivisionByZeroError in PHP 8; check for an empty array first.
Without declare(strict_types=1), PHP may convert scalar arguments silently, such as "5" to 5.

Try it yourself

Predict average([10, 20, 31]).

Reveal answer and reasoning

The sum is 61 and 61 / 3 is 20.333333333333, so that is what echo prints.

PHP Functions