generate.php

<?php
$code = '<?php
$array = [
';

for ($i = 0; $i <= 7; $i++) {
     $code .= "    'key" . chr($i) . "' => 'value_" . $i . "',\n";
}

$code .= '];
print_r($array);
';

file_put_contents('./keys.php', $code);

keys.php

<?php
$array = [
    'key' => 'value_0',
    'key
' => 'value_1',
    'key' => 'value_2',
    'key' => 'value_3',
    'key' => 'value_4',
    'key' => 'value_5',
    'key' => 'value_6',
    'key' => 'value_7',
];
print_r($array);

keys.rb

# -*- encoding: utf-8 -*-

require 'pp'

array = {'key' => 'value_0',
    'key
' => 'value_1',
    'key' => 'value_2',
    'key' => 'value_3',
    'key' => 'value_4',
    'key' => 'value_5',
    'key' => 'value_6',
    'key' => 'value_7'}

pp array

keys_sample.php

<?php
$keys = [];
for ($i = 0x0; $i < 0x20; $i++) {
     $keys[chr($i)] = sprintf('%02s', strtoupper(dechex($i)));
}
print_r($keys);