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No single testing technique is sufficient to ensure software correctness. Drawing on the Swiss Cheese Model, this piece argues for a multi-layered quality strategy in PHP development combining static analysis (Psalm/PHPStan), traditional dynamic testing with PHPUnit, property-based testing, mutation testing, and fuzz testing. Each technique catches a different class of bugs: static analysis finds type errors without execution, unit tests verify specific behaviors, property-based testing explores input spaces automatically, mutation testing validates test suite quality, and fuzzing discovers unknown edge cases. These layers form a circular, reinforcing relationship rather than a strict hierarchy, and each informs and strengthens the others.