Value and reference passing
Most methods passed arguments when they are called. An argument may be a constant or a variable. For example in the expression: Math.sqrt(x); The variable x is passed here.
Pass by Reference means the passing the address itself rather than passing the value and pass by value means passing a copy of the value as an argument.
This is simple enough, however there is an important but simple principle at work here. If a variable is passed, the method receives a copy of the variable's value. The value of the original variable cannot be changed within the method. This seems reasonable because the method only has a copy of the value; it does not have access to the original variable. This process is called pass by value.
pass a variable by reference to a function so the function can modify the variable. The syntax is as follows:
// $a is 6 here
The following things can be passed by reference:
- Variables, i.e. foo($a)
- New statements, i.e. foo(new foobar())
References returned from functions, i.e.:
$a = 5;