PHP

Passing Data

By default, an argument is passed to a function by value. That means that a copy of the data is passed to the function, not the actual data itself.

The arguments (or parameters) of a function can be variables or literals:

If a variable is passed to the function, changing the value of the argument within the function does not change the value of the variable passed to the function.
Arguments exist only for the life of the function-if you call the function several times, the arguments are created afresh each time you call the function, and values they held when the function last ended are not retained.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="EN" lang="EN">
<head>
<title>PHP</title>
<meta Name="Author" Content="Hann So">
</head>
<body>
<p>
<?php
function Add($num1, $num2)
  {
  echo "$num1 + $num2", $num1+$num2;
  }
Add(5, 15);
?>
</p>
</body>
</html>

View the effect