What is a valid variable declaration in PHP?

Answer 1

In PHP, you can declare a variable in several ways.

In the global scope, or within a function, you can use:

• var $variable; // Creates an empty variable
• $variable = {something}; // declares, then assigns, the variable

In the object scope, a property operates like a variable:

• public $variable; // Creates an empty property
• private $variable; // Same thing, but can't be referenced outside the object
• protected $variable; // Similar, but can only be referenced in the object or any object extended by it
• public/private/protected $variable = {something}; // declares, then assigns a default value to, the property
• $this->variable = {something}; // if not declared, this will declare the property and assign the value to it

You can also create object properties from outside the object:

• $object->variable = {something}; // works just like $this->variable

Finally, the arguments to a function are implicitly declared:

• function DoSomething ($variable) { ... } // declares and assigns $variable

Variables in PHP are very flexible, mutable things. This is unlike some other languages that rely on strict type declarations for variables and other code constructs.