Convert an integer byte value into a human-readable file size.

human_filesize.php

<?php

//----------
// Only works with INTEGER values for $bytes.
function human_filesize($bytes, $decimals = 2) {
  $sz = 'BKMGTP';
  $bytes = (int)$bytes;  // This process only works with integer $byte values.
  $factor = floor((strlen($bytes) - 1) / 3); // Determine the correct range.
  $s = $bytes / pow(1024, $factor);  // Knock out the right number of exponents.
  $s = sprintf("%.{$decimals}f", $s) + 0; // Clean up decimals, `+0` removes trailing zeroes.
  return sprintf('%s %s', $s, @$sz[$factor]); // Return the formatted number and unit.
}



// main() -----------------
$tests = array(
	5,  // 5 bytes
	1024 * 5.678, // 5.68 kb
	1024 * 1024 * 7.5,  // 7.5 mb
	1024 * 1024 * 1024 * 10,  // 10 gb
	1024 * 1024 * 1024 * 1024 * 15.004,  // 15.02 tb
	1024 * 1024 * 1024 * 1024 * 1024 * 6.222,  // 6.22 pb
);

foreach ($tests as $b) {
	echo "$b --> " . human_filesize($b) . PHP_EOL;
}

Output:

5 --> 5 B
5814.272 --> 5.68 K
7864320 --> 7.5 M
10737418240 --> 10 G
16497072463151 --> 15 T
7.0053492203748E+15 --> 6.22 P