ARSORT(3) 1 ARSORT(3)arsort - Sort an array in reverse order and maintain index associationSYNOPSIS
bool arsort (array &$array, [int $sort_flags = SORT_REGULAR])
DESCRIPTION
This function sorts an array such that array indices maintain their correlation with the array elements they are associated with.
This is used mainly when sorting associative arrays where the actual element order is significant.
PARAMETERS
o $array
- The input array.
o $sort_flags
- You may modify the behavior of the sort using the optional parameter $sort_flags, for details see sort(3).
RETURN VALUES
Returns TRUE on success or FALSE on failure.
EXAMPLES
Example #1
arsort(3) example
<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");
arsort($fruits);
foreach ($fruits as $key => $val) {
echo "$key = $val
";
}
?>
The above example will output:
a = orange
d = lemon
b = banana
c = apple
The fruits have been sorted in reverse alphabetical order, and the index associated with each element has been maintained.
SEE ALSO asort(3), The comparison of array sorting functions.
PHP Documentation Group ARSORT(3)
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USORT(3) 1 USORT(3)usort - Sort an array by values using a user-defined comparison functionSYNOPSIS
bool usort (array &$array, callable $value_compare_func)
DESCRIPTION
This function will sort an array by its values using a user-supplied comparison function. If the array you wish to sort needs to be sorted
by some non-trivial criteria, you should use this function.
Note
If two members compare as equal, their relative order in the sorted array is undefined.
Note
This function assigns new keys to the elements in $array. It will remove any existing keys that may have been assigned, rather than
just reordering the keys.
PARAMETERS
o $array
- The input array.
o $value_compare_func
- The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to
be respectively less than, equal to, or greater than the second.
int callback (mixed $a, mixed $b)
Caution
Returning non-integer values from the comparison function, such as float, will result in an internal cast to integer of the
callback's return value. So values such as 0.99 and 0.1 will both be cast to an integer value of 0, which will compare such
values as equal.
RETURN VALUES
Returns TRUE on success or FALSE on failure.
EXAMPLES
Example #1
usort(3) example
<?php
function cmp($a, $b)
{
if ($a == $b) {
return 0;
}
return ($a < $b) ? -1 : 1;
}
$a = array(3, 2, 5, 6, 1);
usort($a, "cmp");
foreach ($a as $key => $value) {
echo "$key: $value
";
}
?>
The above example will output:
0: 1
1: 2
2: 3
3: 5
4: 6
Note
Obviously in this trivial case the sort(3) function would be more appropriate.
Example #2
usort(3) example using multi-dimensional array
<?php
function cmp($a, $b)
{
return strcmp($a["fruit"], $b["fruit"]);
}
$fruits[0]["fruit"] = "lemons";
$fruits[1]["fruit"] = "apples";
$fruits[2]["fruit"] = "grapes";
usort($fruits, "cmp");
while (list($key, $value) = each($fruits)) {
echo "$fruits[$key]: " . $value["fruit"] . "
";
}
?>
When sorting a multi-dimensional array, $a and $b contain references to the first index of the array.
The above example will output:
$fruits[0]: apples
$fruits[1]: grapes
$fruits[2]: lemons
Example #3
usort(3) example using a member function of an object
<?php
class TestObj {
var $name;
function TestObj($name)
{
$this->name = $name;
}
/* This is the static comparing function: */
static function cmp_obj($a, $b)
{
$al = strtolower($a->name);
$bl = strtolower($b->name);
if ($al == $bl) {
return 0;
}
return ($al > $bl) ? +1 : -1;
}
}
$a[] = new TestObj("c");
$a[] = new TestObj("b");
$a[] = new TestObj("d");
usort($a, array("TestObj", "cmp_obj"));
foreach ($a as $item) {
echo $item->name . "
";
}
?>
The above example will output:
b
c
d
Example #4
usort(3) example using a closure to sort a multi-dimensional array
<?php
$array[0] = array('key_a' => 'z', 'key_b' => 'c');
$array[1] = array('key_a' => 'x', 'key_b' => 'b');
$array[2] = array('key_a' => 'y', 'key_b' => 'a');
function build_sorter($key) {
return function ($a, $b) use ($key) {
return strnatcmp($a[$key], $b[$key]);
};
}
usort($array, build_sorter('key_b'));
foreach ($array as $item) {
echo $item['key_a'] . ', ' . $item['key_b'] . "
";
}
?>
The above example will output:
y, a
x, b
z, c
SEE ALSO uasort(3), The comparison of array sorting functions.
PHP Documentation Group USORT(3)