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# What References Do

PHP references allow you to make two variables to refer to the same content. Meaning, when you do:

    $a =& $b

it means that `$a` and `$b` point to the same variable.

> Note: `$a` and `$b` are completely equal here, that's not `$a` is pointing to `$b` or vice versa, that's `$a` and `$b` pointing to the same place.

The same syntax can be used with functions, that return references, and with `new` operator (in PHP 4.0.4 and later):

    $bar =& new fooclass();
    $foo =& find_var ($bar);

> Note: Not using the `&` operator causes a copy of the object to be made. If you use `$this` in the class it will operate on the current instance of the class. The assignment without `&` will copy the instance (i.e. the object) and `$this` will operate on the copy, which is not always what is desired. Usually you want to have a single instance to work with, due to performance and memory consumption issues.

> While you can use the `@` operator to mute any errors in the constructor when using it as `@new`, this does not work when using the `&new` statement. This is a limitation of the Zend Engine and will therefore result in a parser error.

The second thing references do is to pass variables by-reference. This is done by making a local variable in a function and a variable in the calling scope reference to the same content. Example:

    function foo (&$var)
    {
        $var++;
    }

    $a=5;
    foo ($a);

will make `$a` to be 6. This happens because in the function `foo` the variable `$var` refers to the same content as `$a`. See also more detailed explanations about passing by reference.

The third thing reference can do is return by reference.

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