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Editing: README.namespaces
Design ====== Main assumption of the model is that the problem that we are to solve is the problem of the very long class names in PHP libraries. We would not attempt to take autoloader's job or create packaging model - only make names manageable. Namespaces are defined the following way: Zend/DB/Connection.php: <?php namespace Zend\DB; class Connection { } function connect() { } ?> Namespace definition does the following: All class and function names inside are automatically prefixed with namespace name. Inside namespace, local name always takes precedence over global name. Several files may be using the same namespace. The namespace declaration statement must be the very first statement in the file. The only exception is "declare" statement that can be used before. Every class and function in a namespace can be referred to by the full name - e.g. Zend\DB\Connection or Zend\DB\connect - at any time. <?php require 'Zend/Db/Connection.php'; $x = new Zend\DB\Connection; Zend\DB\connect(); ?> Namespace or class name can be imported: <?php require 'Zend/Db/Connection.php'; use Zend\DB; use Zend\DB\Connection as DbConnection; $x = new Zend\DB\Connection(); $y = new DB\connection(); $z = new DbConnection(); DB\connect(); ?> The use statement only defines name aliasing. It may create name alias for namespace or class. The simple form of statement "use A\B\C\D;" is equivalent to "use A\B\C\D as D;". The use statement can be used at any time in the global scope (not inside function/class) and takes effect from the point of definition down to the end of file. It is recommended however to place the use statements at the beginning of the file. The use statements have effect only on the file where they appear. The special "empty" namespace (\ prefix) is useful as explicit global namespace qualification. All class and function names started from \ interpreted as global. <?php namespace A\B\C; $con = \mysql_connect(...); ?> A special constant __NAMESPACE__ contains the name of the current namespace. It can be used to construct fully-qualified names to pass them as callbacks. <?php namespace A\B\C; function foo() { } set_error_handler(__NAMESPACE__ . "\foo"); ?> In global namespace __NAMESPACE__ constant has the value of empty string. Names inside namespace are resolved according to the following rules: 1) all qualified names are translated during compilation according to current import rules. So if we have "use A\B\C" and then "C\D\e()" it is translated to "A\B\C\D\e()". 2) unqualified class names translated during compilation according to current import rules. So if we have "use A\B\C" and then "new C()" it is translated to "new A\B\C()". 3) inside namespace, calls to unqualified functions that are defined in current namespace (and are known at the time the call is parsed) are interpreted as calls to these namespace functions. 4) inside namespace, calls to unqualified functions that are not defined in current namespace are resolved at run-time. The call to function foo() inside namespace (A\B) first tries to find and call function from current namespace A\B\foo() and if it doesn't exist PHP tries to call internal function foo(). Note that using foo() inside namespace you can call only internal PHP functions, however using \foo() you are able to call any function from the global namespace. 5) unqualified class names are resolved at run-time. E.q. "new Exception()" first tries to use (and autoload) class from current namespace and in case of failure uses internal PHP class. Note that using "new A" in namespace you can only create class from this namespace or internal PHP class, however using "new \A" you are able to create any class from the global namespace. 6) Calls to qualified functions are resolved at run-time. Call to A\B\foo() first tries to call function foo() from namespace A\B, then it tries to find class A\B (__autoload() it if necessary) and call its static method foo() 7) qualified class names are interpreted as class from corresponding namespace. So "new A\B\C()" refers to class C from namespace A\B. Examples -------- <?php namespace A; foo(); // first tries to call "foo" defined in namespace "A" // then calls internal function "foo" \foo(); // calls function "foo" defined in global scope ?> <?php namespace A; new B(); // first tries to create object of class "B" defined in namespace "A" // then creates object of internal class "B" new \B(); // creates object of class "B" defined in global scope ?> <?php namespace A; new A(); // first tries to create object of class "A" from namespace "A" (A\A) // then creates object of internal class "A" ?> <?php namespace A; B\foo(); // first tries to call function "foo" from namespace "A\B" // then calls method "foo" of internal class "B" \B\foo(); // first tries to call function "foo" from namespace "B" // then calls method "foo" of class "B" from global scope ?> The worst case if class name conflicts with namespace name <?php namespace A; A\foo(); // first tries to call function "foo" from namespace "A\A" // then tries to call method "foo" of class "A" from namespace "A" // then tries to call function "foo" from namespace "A" // then calls method "foo" of internal class "A" \A\foo(); // first tries to call function "foo" from namespace "A" // then calls method "foo" of class "A" from global scope ?> TODO ==== * Support for namespace constants? * performance problems - calls to internal functions in namespaces are slower, because PHP first looks for such function in current namespace - calls to static methods are slower, because PHP first tries to look for corresponding function in namespace * Extend the Reflection API? * Add ReflectionNamespace class + getName() + getClasses() + getFunctions() + getFiles() * Add getNamespace() methods to ReflectionClass and ReflectionFunction * Rename namespaces to packages?
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