Convert bytes to human readable format

human_bytes.php

<?php 
/**
 * Convert bytes to human readable format
 *
 * @param integer $bytes Size in bytes to convert
 * @param integer $precision
 *
 * @return string
 */
function prefix_human_bytes( $bytes, $precision = 2 ) {
	$kilobyte = 1024;
	$megabyte = $kilobyte * 1024;
	$gigabyte = $megabyte * 1024;
	$terabyte = $gigabyte * 1024;

	if ( ( $bytes >= 0 ) && ( $bytes < $kilobyte ) ) {
		return $bytes . ' B';

	} elseif ( ( $bytes >= $kilobyte ) && ( $bytes < $megabyte ) ) {
		return round( $bytes / $kilobyte, $precision ) . ' KB';

	} elseif ( ( $bytes >= $megabyte ) && ( $bytes < $gigabyte ) ) {
		return round( $bytes / $megabyte, $precision ) . ' MB';

	} elseif ( ( $bytes >= $gigabyte ) && ( $bytes < $terabyte ) ) {
		return round( $bytes / $gigabyte, $precision ) . ' GB';

	} elseif ( $bytes >= $terabyte ) {
		return round( $bytes / $terabyte, $precision ) . ' TB';
	} else {
		return $bytes . ' B';
	}
}