Many syntax constructs in PHP are implemented via referencing mechanisms, so everything mentioned herein about reference binding also applies to these constructs. Some constructs, like passing and returning by reference, are mentioned above. Other constructs that use references are:
When you declare a variable as global $var you are in fact creating reference to a global variable. That means, this is the same as:
<?php $var =& $GLOBALS["var"]; ?>
This also means that unsetting $var won't unset the global variable.
In an object method, $this is always a reference to the called object.
Variables in PHP
Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive. Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.
Is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML