Lotion pumps are commonly used to dispense liquid products like lotions, creams, and other cosmetic or personal care items. They typically consist of a pump mechanism, a dip tube (a long tube that reaches the bottom of the container), and a closure.

To prevent overflow, lotion pumps often have built-in features that control the amount of product dispensed with each pump. Here are some mechanisms commonly used to prevent overflow:

1. Metered Dose Dispensing: Some lotion pumps are designed to dispense a specific amount of product with each pump. This metered dose ensures that the user receives a consistent and controlled amount of lotion, reducing the risk of overflow.

2. Check Valve: Lotion pumps may include a check valve mechanism. This valve allows the product to flow out of the container when the pump is depressed but prevents it from flowing back into the container when the pump is released. This helps to minimize the risk of overflow and keeps the lotion contained within the dip tube.

3. Spring Mechanism: The pump may have a spring-loaded mechanism that controls the amount of product released. When the pump is pressed, the spring compresses, allowing lotion to be dispensed. When the pressure is released, the spring pushes back, closing off the flow of lotion and preventing overflow.

4. Anti-siphon Valve: Some pumps are equipped with an anti-siphon valve. This valve prevents the product from siphoning back into the container, even if the dip tube is submerged in liquid, which can help prevent overflow.

5. Restricted Flow: The pump design may include a restricted flow path, which limits the speed at which the lotion is dispensed. Slowing down the flow can help prevent spillage and overflow.

Please note that the specific features of the "plastic PP shiny gold lotion pump" may vary based on its design and manufacturer. The best way to understand how a particular lotion pump prevents overflow is to check the product's specifications or reach out to the manufacturer for detailed information.