Core PHP Programming: Using PHP to Build Dynamic Web Sites

Arguments

When declaring a function, you may declare arguments inside the parentheses, each separated by a comma. The arguments must be preceded by a dollar sign. They become variables inside the function. When the function is called, it expects values to be passed that will fill the arguments in the order declared.

Arguments, by default, copy the passed value into the local variable. If the variable is preceded by the & operator, the variable instead becomes an alias for the passed variable. This is commonly referred to as a variable reference. Changes made to referenced variables change the original.

To demonstrate this idea, imagine we wanted a function that stripped commas from numbers. That way if we got something like "10,000" from an input ...