Convert int to arbitrary base with custom alphabet

base_encode.php

<?php

echo base_encode('0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', 100500) . PHP_EOL;

function base_encode($alphabet, $number, $suffix = '') {
	$base = strlen($alphabet);
	if ($number >= $base) {
		$div = intval($number / $base); // For php7: intdiv($number, $base);
		$mod = $number % $base;
		return base_encode($alphabet, $div, $alphabet[$mod] . $suffix);
	} else {
		return $alphabet[$number] . $suffix;
	}
}