Functions · Lesson 7 of 9

Anonymous Functions

Create a closure when behavior is useful as a value.

Lesson

An anonymous function has no declared name and can be stored or passed as a callback. A closure captures outside variables explicitly with use; capture by value unless mutation is intentional. Named functions are often clearer for behavior reused in several places. This closure captures a tax rate and calculates the total for one amount. Further guidance Treat a function as a small contract: name its inputs, state what it returns, and avoid hidden dependencies. Test a representative value and an edge case. Keep a function focused; callers should decide how to display a returned result or handle a reported failure. Practice task: Create a fresh example for Anonymous Functions. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.

Code examples

Anonymous Functions

PHP

$rate = 0.1;
$withTax = function (float $amount) use ($rate): float {
    return $amount * (1 + $rate);
};
echo $withTax(100);

Expected output

Key points

Create a closure when behavior is useful as a value.
Keep inputs, return values, and side effects explicit.
Prefer focused functions that are easy to test independently.

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