How to sort an array based on a value - php

Question

$arr['a']['studentname'] = "john";
$arr['b']['studentname'] = "stefen";
$arr['c']['studentname'] = "alex";
is it possible to sort using user defined functions:
usort( $arr )
uasort( $arr )
uksort( $arr )
so based on value which i need to pass, the array should be sorted!
expected output:
if the current value then
Array
(
[c] => Array
(
[studentname] => alex
)
[a] => Array
(
[studentname] => john
)
[b] => Array
(
[studentname] => stefen
)
)
if the current value then
Array
(
[b] => Array
(
[studentname] => stefen
)
[a] => Array
(
[studentname] => john
)
[c] => Array
(
[studentname] => alex
)
)
thanks in advance

Answer 1

If I understood the question, you can use a simple string compare callback:
$arr['a']['studentname'] = "john";
$arr['b']['studentname'] = "stefen";
$arr['c']['studentname'] = "alex";
// A-Z
uasort($arr, function($a, $b) {
return strcmp($a['studentname'], $b['studentname']);
});
print_r($arr);
// Z-A
uasort($arr, function($a, $b) {
return strcmp($b['studentname'], $a['studentname']);
});
print_r($arr);

Answer 2

Try this:
For PHP version > 5.3:
$arr['a']['studentname'] = "john";
$arr['b']['studentname'] = "stefen";
$arr['c']['studentname'] = "alex";
uasort($arr, function($a, $b) {
return strcmp($a['studentname'], $b['studentname']);
});
For PHP version < 5.3:
$arr['a']['studentname'] = "john";
$arr['b']['studentname'] = "stefen";
$arr['c']['studentname'] = "alex";
function sort_by($a, $b) {
return strcmp($a['studentname'], $b['studentname']);
}
uasort($arr, 'sort_by');