note 86210 added to function.array-unique
| From: | florianatboxdotnet at osu1 dot php dot net | Date: | Wed, 08 Oct 2008 08:29:38 +0000 |
| Subject: | note 86210 added to function.array-unique | ||
| Groups: | php.notes | ||
| Request: | Send a blank email to php-notes+get-145154@lists.php.net to get a copy of this message | ||
I came across one limitation of array_unique: it doesn't work properly if you have arrays
inside your main array.
The reason is that to compare two values, the function tests if (string) $value1 == (string)
$value2. So if $value1 and $value2 are both arrays, the function will evaluate the test to
'Array' == 'Array', and decide that the $values are repeated even if the arrays
are different.
So a work around is to find a better conversion of an array to a string, which can be done with
json:
<?php
print "define an array with repeated scalar '1' and repeated
'array(1)':";
$a_not_unique = array(
'a' => 1,
'b' => 1,
'c' => 2,
'd' => array(1),
'e' => array(1),
'f' => array(2),
);
print_r($a_not_unique);
print "try to use simply array_unique, which will not work since it exludes
'array(2)':";
$a_unique_wrong = array_unique($a_not_unique);
print_r($a_unique_wrong);
print "convert to json before applying array_unique, and convert back to array, which will
successfully keep 'array(2)':";
$a_unique_right = $a_not_unique;
array_walk($a_unique_right, create_function('&$value,$key', '$value =
json_encode($value);'));
$a_unique_right = array_unique($a_unique_right);
array_walk($a_unique_right, create_function('&$value,$key', '$value =
json_decode($value, true);'));
print_r($a_unique_right);
?>
Results:
define an array with repeated scalar '1' and repeated 'array(1)':
Array
(
[a] => 1
[b] => 1
[c] => 2
[d] => Array
(
[0] => 1
)
[e] => Array
(
[0] => 1
)
[f] => Array
(
[0] => 2
)
)
try to use simply array_unique, which will not work since it exludes 'array(2)':
Array
(
[a] => 1
[c] => 2
[d] => Array
(
[0] => 1
)
)
convert to json before applying array_unique, and convert back to array, which will successfully
keep 'array(2)':
Array
(
[a] => 1
[c] => 2
[d] => Array
(
[0] => 1
)
[f] => Array
(
[0] => 2
)
)
----
Server IP: 64.71.164.2
Probable Submitter: 75.149.61.49
----
Manual Page -- http://www.php.net/manual/en/function.array-unique.php
Edit -- https://master.php.net/note/edit/86210
Del: integrated -- https://master.php.net/note/delete/86210/integrated
Del: useless -- https://master.php.net/note/delete/86210/useless
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Del: non-english -- https://master.php.net/note/delete/86210/non-english
Del: in docs -- https://master.php.net/note/delete/86210/in+docs
Del: other reasons-- https://master.php.net/note/delete/86210
Reject -- https://master.php.net/note/reject/86210
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