Namespaces and dynamic language features

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

PHP's implementation of namespaces is influenced by its dynamic nature as a programming language. Thus, to convert code like the following example into namespaced code:

Example #1 Dynamically accessing elements

example1.php:

<?php
class classname
{
function
__construct()
{
echo
__METHOD__,"\n";
}
}
function
funcname()
{
echo
__FUNCTION__,"\n";
}
const
constname = "global";

$a = 'classname';
$obj = new $a; // prints classname::__construct
$b = 'funcname';
$b(); // prints funcname
echo constant('constname'), "\n"; // prints global
?>
One must use the fully qualified name (class name with namespace prefix). Note that because there is no difference between a qualified and a fully qualified Name inside a dynamic class name, function name, or constant name, the leading backslash is not necessary.

Example #2 Dynamically accessing namespaced elements

<?php
namespace namespacename;
class
classname
{
function
__construct()
{
echo
__METHOD__,"\n";
}
}
function
funcname()
{
echo
__FUNCTION__,"\n";
}
const
constname = "namespaced";

/* note that if using double quotes, "\\namespacename\\classname" must be used */
$a = '\namespacename\classname';
$obj = new $a; // prints namespacename\classname::__construct
$a = 'namespacename\classname';
$obj = new $a; // also prints namespacename\classname::__construct
$b = 'namespacename\funcname';
$b(); // prints namespacename\funcname
$b = '\namespacename\funcname';
$b(); // also prints namespacename\funcname
echo constant('\namespacename\constname'), "\n"; // prints namespaced
echo constant('namespacename\constname'), "\n"; // also prints namespaced
?>

Be sure to read the note about escaping namespace names in strings.