Functions · Lesson 3 of 9

Function Parameters

Pass data into a function through typed parameters.

Lesson

Parameters name the input values a function requires. Type declarations communicate expectations and can catch mistakes earlier. Pass values by reference only when the function intentionally must change the caller's variable; ordinary value parameters are easier to reason about. The example accepts two typed inputs instead of reading global variables. 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 Function Parameters. 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

Function Parameters

PHP

function fullName(string $first, string $last): string
{
    return $first . ' ' . $last;
}
echo fullName('Ada', 'Lovelace');

Expected output

Ada Lovelace

Key points

Pass data into a function through typed parameters.
Keep inputs, return values, and side effects explicit.
Prefer focused functions that are easy to test independently.

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