Closures and 'use'

Part of the Logic & Flow section of Coddy's PHP journey — lesson 2 of 68.

By default, anonymous functions can only access variables that are passed to them as parameters. But what if you need your closure to access a variable from the surrounding scope? This is where the use keyword comes in.

The use keyword allows a closure to "capture" variables from its parent scope and use them inside the function:

<?php
$message = "Welcome";

$greeting = function($name) use ($message) {
    echo $message . ", " . $name . "!";
};

$greeting("Bob");  // Outputs: Welcome, Bob!
?>

Notice how $message is defined outside the function, but by including use ($message) after the parameter list, the closure can access and use that variable. You can capture multiple variables by separating them with commas: use ($var1, $var2).

This feature makes closures much more powerful, allowing them to work with data from their surrounding context while still maintaining the flexibility of anonymous functions.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Challenge

Easy

Create an anonymous function that captures a discount percentage from the surrounding scope using the use keyword. The function should take a price as a parameter and return the final price after applying the discount.

You will receive two inputs: the discount percentage and the original price. Read both inputs, create a closure that captures the discount percentage, call the closure with the price, and print the final price after discount.

Input format: Two lines - first line contains the discount percentage (a number), second line contains the original price (a number which may contain decimals)

Expected output: The final price after applying the discount

Cheat sheet

The use keyword allows closures to capture variables from their parent scope:

<?php
$message = "Welcome";

$greeting = function($name) use ($message) {
    echo $message . ", " . $name . "!";
};

$greeting("Bob");  // Outputs: Welcome, Bob!
?>

You can capture multiple variables by separating them with commas: use ($var1, $var2).

Try it yourself

<?php
// Read inputs
$discount = floatval(fgets(STDIN));
$price = floatval(fgets(STDIN));

// TODO: Create an anonymous function that captures the discount percentage using 'use'
// The function should take a price parameter and return the final price after discount


// TODO: Call the closure with the price and store the result


// Output the final price
echo $finalPrice;
?>

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Closures and 'use'

Cheat sheet

All lessons in Logic & Flow