Object-Oriented PHP · Lesson 3 of 14

Objects

Create an instance of a class and call its behavior.

Lesson

An object is an instance of a class. Create one with new, then access its public methods with ->. Two instances can hold independent state. Depend on an object's public contract rather than reaching into its internal representation. This example creates two independent objects with their own names. Further guidance Give an object one clear responsibility and protect state that must satisfy a rule. Prefer a small public contract and composition for replaceable collaborators; use inheritance only for a genuine subtype. Test behavior through public methods instead of relying on internal implementation details. Practice task: Create a fresh example for Objects. 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

Objects

PHP

class Badge
{
    public function __construct(public string $label) {}
}
$first = new Badge('PHP');
$second = new Badge('SQL');
echo $first->label, ', ', $second->label;

Expected output

PHP, SQL

Key points

Create an instance of a class and call its behavior.
Protect object invariants behind a small public API.
Prefer composition unless inheritance expresses a genuine subtype.

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