Conditionals · Lesson 2 of 6

if...else

Choose exactly one of two paths with if and else.

Lesson

Use else for the alternative path when an if condition is false. Both branches should describe the same decision, such as whether a value is within a validated threshold. If branches become large, extract the work into functions to keep the control flow readable. This example handles both possible outcomes of a simple stock check. Further guidance Test each branch with a normal value, a boundary value, and an unexpected value. Order range checks from specific to broad, make the fallback behavior intentional, and keep related decisions readable. A condition should use validated data rather than an untrusted request value directly. Practice task: Create a fresh example for if...else. 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

if...else

PHP

$stock = 0;
if ($stock > 0) {
    echo 'In stock';
} else {
    echo 'Sold out';
}

Expected output

Sold out

Key points

Choose exactly one of two paths with if and else.
Test boundary cases for every conditional branch.
Keep fallback behavior explicit and use validated values.

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