- var_dump: documentation ( source)
- ksort: documentation ( source)
<?php
$a = array('a' => 10, 'z' => 10, 'c' => 10, 'b' => 11, 'd' => 10);
$b = array();
foreach($a as $k => $v) $b[$v][] = $k;
ksort($b);
$a = array();
foreach($b as $k => $v) {
foreach($v as $i) $a[$i] = $k;
}
var_dump($a);