Why you need to be careful when using base64 encoding to get a random key from random_bytes()

base64-random-keys.php

<?php

$characters = [];

for ($k = 0; $k < 500000; $k++) {

	$key = base64_encode(random_bytes(32)); // 32 bytes results in "=" padding; try changing to 30 to fix.

	foreach (str_split($key) as $c) {
		if (!isset($characters[$c])) {
			$characters[$c] = 0;
		}
		$characters[$c]++;
	}

}

$characters = array_filter($characters, function($value) {
		return ($value > 343750); // ((((33/3)*4)*500000)/64) = 343750, everything else is about ~327000
	});

ksort($characters, SORT_STRING);

print_r($characters);

// For 32:
//  0 = 358332
//  4 = 359777
//  8 = 360089
//  A = 359424
//  E = 358689
//  I = 360217
//  M = 359899
//  Q = 360058
//  U = 359104
//  Y = 359601
//  c = 358607
//  g = 358158
//  k = 359594
//  o = 359204
//  s = 358803
//  w = 359793
//  = = 500000 *

// For 31:
//  A = 445603
//  Q = 445572
//  g = 445780
//  w = 445876
//  = = 1000000 *

?>