Wednesday, December 12. 2007
 |
 |
 |
 |
Posted by Frank Kleine
in
Planet PHP Comment (1) Trackback (1) |
 |
 |
 |
 |
Tricky namespaces
Today on php-internals David Zülke posted an interesting example with namespaces which made me think about the result of the small example. Well, my first guess was not right as my experiments showed. Therefore I tried different versions of the example to see the impact of namespace and use declarations. But first, the example:
Version 1, the original from David's posting:
Result:
More after the break...
Name/Space/DateTime.php
namespace Name::Space;
class DateTime {}
Name/Space/Ship.php
namespace Name::Space;
class Ship {
public static function __autoload($className) {
echo "loading $className\n";
// ... autoloader, can load Name::Space::DateTime
}
}
somestuff.php
function someStuffWeDoNotHaveControlOver() {
$foo = new Name::Space::DateTime();
var_dump($foo);
// ...
}
setup.php
require_once('Name/Space/Ship.php');
spl_autoload_register(array('Name::Space::Ship', '__autoload'));
Version 1, the original from David's posting:
require_once('setup.php');
use Name::Space;
$d = new DateTime();
var_dump($d);
require_once('somestuff.php'); // assumed to be here, was missing in the given example
someStuffWeDoNotHaveControlOver();
$d = new DateTime();
var_dump($d);
Result:
object(DateTime)#1 (0) {
}
loading Name::Space::DateTime
object(Name::Space::DateTime)#2 (0) {
}
object(DateTime)#2 (0) {
}
More after the break...
Version 2, moved the inclusion of somestuff.php:
Same result as version 1.
Version 3, use Name::Space means use Name::Space as Space:
Result:
Version 4, lets put our example into its own namespace:
Result:
Version 5, version 3 with example in its own namespace:
Result:
Version 6, create the shortcut for the class instead for the namespace only:
Same result as version 5, is equivalent.
If you want to create an instance of PHP's DateTime class here you would need to do new ::DateTime:
Result:
Consequences? You will need strict rules for the usage of "use" in your project. Mixing different styles will result in difficulties to see what the code does. Additionally it seems to be a good idea to always do "::ClassName" when accessing global classes as it makes a clear statement about the source of the class.
require_once('setup.php');
require_once('somestuff.php');
use Name::Space;
$d = new DateTime();
var_dump($d);
someStuffWeDoNotHaveControlOver();
$d = new DateTime();
var_dump($d);
Same result as version 1.
Version 3, use Name::Space means use Name::Space as Space:
require_once('setup.php');
require_once('somestuff.php');
use Name::Space;
$d = new Space::DateTime();
var_dump($d);
someStuffWeDoNotHaveControlOver();
$d = new Space::DateTime();
var_dump($d);
Result:
loading Name::Space::DateTime
object(Name::Space::DateTime)#1 (0) {
}
object(Name::Space::DateTime)#2 (0) {
}
object(Name::Space::DateTime)#2 (0) {
}
Version 4, lets put our example into its own namespace:
namespace foo;
require_once('setup.php');
require_once('somestuff.php');
use Name::Space;
$d = new DateTime();
var_dump($d);
// we need to prepend the function name with ::
// else PHP will try to call foo::someStuffWeDoNotHaveControlOver() which does not exist
::someStuffWeDoNotHaveControlOver();
$d = new DateTime();
var_dump($d);
Result:
object(DateTime)#1 (0) {
}
loading Name::Space::DateTime
object(Name::Space::DateTime)#2 (0) {
}
object(DateTime)#2 (0) {
}
Version 5, version 3 with example in its own namespace:
namespace foo;
require_once('setup.php');
require_once('somestuff.php');
use Name::Space;
$d = new Space::DateTime();
var_dump($d);
// we need to prepend the function name with ::
// else PHP will try to call foo::someStuffWeDoNotHaveControlOver() which does not exist
::someStuffWeDoNotHaveControlOver();
$d = new Space::DateTime();
var_dump($d);
Result:
loading Name::Space::DateTime
object(Name::Space::DateTime)#1 (0) {
}
object(Name::Space::DateTime)#2 (0) {
}
object(Name::Space::DateTime)#2 (0) {
}
Version 6, create the shortcut for the class instead for the namespace only:
namespace foo;
require_once('setup.php');
require_once('somestuff.php');
use Name::Space::DateTime;
$d = new DateTime();
var_dump($d);
// we need to prepend the function name with ::
// else PHP will try to call foo::someStuffWeDoNotHaveControlOver() which does not exist
::someStuffWeDoNotHaveControlOver();
$d = new DateTime();
var_dump($d);
Same result as version 5, is equivalent.
If you want to create an instance of PHP's DateTime class here you would need to do new ::DateTime:
namespace foo;
require_once('setup.php');
require_once('somestuff.php');
use Name::Space::DateTime;
$d = new ::DateTime();
var_dump($d);
// we need to prepend the function name with ::
// else PHP will try to call foo::someStuffWeDoNotHaveControlOver() which does not exist
::someStuffWeDoNotHaveControlOver();
$d = new ::DateTime();
var_dump($d);
Result:
object(DateTime)#1 (0) {
}
loading Name::Space::DateTime
object(Name::Space::DateTime)#2 (0) {
}
object(DateTime)#2 (0) {
}
Consequences? You will need strict rules for the usage of "use" in your project. Mixing different styles will result in difficulties to see what the code does. Additionally it seems to be a good idea to always do "::ClassName" when accessing global classes as it makes a clear statement about the source of the class.
Calendar
|
July '08 | |||||
| Mon | Tue | Wed | Thu | Fri | Sat | Sun |
| 1 | 2 | 3 | 4 | 5 | 6 | |
| 7 | 8 | 9 | 10 | 11 | 12 | 13 |
| 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 21 | 22 | 23 | 24 | 25 | 26 | 27 |
| 28 | 29 | 30 | 31 | |||
Categories
Quicksearch
Blogs we read...
Syndicate This Blog
Blog Administration
So I put down this namespace examples together last night. But, what's happening in the examples regarding to resolution rules? (I won't post the code here again, have a look at the last entry for the example code.) Version 1 and 2 two are the same, th
Tracked: Dec 12, 10:16