PHP is very rich in terms of Built-in functions. there are more than 1000 built-in functions in PHP. To use those functions we just need to call them as per our requirement like, var_dump, fopen(), print_r(), gettype() and so on.
The parameters work like placeholder variables within a function; they're replaced at run time by the values (known as argument) provided to the function at the time of execution
Sum of the two numbers 18 and 2 is : 20
This means that a reference to the variable is manipulated by the function rather than a copy of the variable's value
Original Value is 13 Original Value is 18
The return keyword is used to return value back to the part of program, from where it was called.a
The product is: 10