- array_map: documentation ( source)
- var_dump: documentation ( source)
- array_combine: documentation ( source)
- array_keys: documentation ( source)
<?php
$foo = [
'a' => '1',
'b' => '1',
'c' => '2',
];
$bar = array_map(function($v) {
return '#' . $v;
}, array_combine(array_keys($foo), array_keys($foo)));
$foo_new = array_combine($bar, $bar);
var_dump($foo_new);