What are common reasons for a custom function's return statement not displaying any results in PHP?

If a custom function's return statement is not displaying any results in PHP, it could be due to the function not being called or the return value not being echoed or stored in a variable after the function call. To solve this issue, make sure to call the function and either echo the return value or assign it to a variable for further use.

// Define a custom function that returns a value
function customFunction() {
    return "Hello, World!";
}

// Call the function and echo the return value
echo customFunction();