Req #51229 [Com]: consecutives sorting with usort and uasort
Edit report at http://bugs.php.net/bug.php?id=51229&edit=1
ID: 51229
Comment by: peter at f-is dot eu
Reported by: kanea at free dot fr
Summary: consecutives sorting with usort and uasort
Status: Open
Type: Feature/Change Request
Package: Arrays related
Operating System: All
PHP Version: 5.2.13
New Comment:
This behavior is documented:
"Note: If two members compare as equal, their order in the sorted array
is undefined."
You should adapt your comparison function so it checks on both a AND b,
in one function.
Previous Comments:
------------------------------------------------------------------------
[2010-03-07 17:52:45] kanea at free dot fr
Description:
------------
on an array with collection of the same object
the object have 2 property a et b
Exemple:
[
object:{a=3, b=2}
object:{a=0, b=2}
object:{a=2, b=3}
object:{a=1, b=2}
If you make a first sort with the good fonction and usort on property a,
you obtain
[
object:{a=0, b=2}
object:{a=1, b=2}
object:{a=2, b=3}
object:{a=3, b=2}
]
The result is that you intend
Now if you make a second sort with another function and usort on
property b, you obtain
[
object:{a=3, b=2}
object:{a=1, b=2}
object:{a=0, b=2}
object:{a=2, b=3}
]
The result is not you can wait. I think that's because the read of the
array is make in inverse way.
A possible solution is to mark the placed elements. And not move
elements not tested before or after them the marked element.
Best Regards
Test script:
---------------
<?php
function compa($a, $b){ if($a['a']>$b['a']) return 1; else return
($a['a']<$b['a'])?-1:0; }
function compb($a, $b){ if($a['b']>$b['b']) return 1; else return
($a['b']<$b['b'])?-1:0; }
$a = array(array('a'=>1, 'b'=>2), array('a'=>2,
'b'=>3), array('a'=>3,
'b'=>2), array('a'=>0, 'b'=>2), array('a'=>4,
'b'=>2));
usort($a, 'compa');
print_r($a);
usort($a, 'compb');
print_r($a);
?>
Expected result:
----------------
Array
(
[0] => Array
(
[a] => 0
[b] => 2
)
[1] => Array
(
[a] => 1
[b] => 2
)
[2] => Array
(
[a] => 3
[b] => 2
)
[3] => Array
(
[a] => 2
[b] => 3
)
)
Actual result:
--------------
Array
(
[0] => Array
(
[a] => 3
[b] => 2
)
[1] => Array
(
[a] => 1
[b] => 2
)
[2] => Array
(
[a] => 0
[b] => 2
)
[3] => Array
(
[a] => 2
[b] => 3
)
)
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=51229&edit=1
Thread (3 messages)