This PHP code defines a function called humanlyFileSize that is used to convert a file size in bytes into a human-readable format with size suffixes (e.g., KB, MB, GB).

humanlyFileSize.php

<?php
// Define a function named humanlyFileSize that takes two parameters:
// $bytes - the file size in bytes
// $decimals (optional) - the number of decimal places to include in the result (default is 2)
function humanlyFileSize($bytes, $decimals = 2) {
    // Define a string $sz containing the size suffixes for bytes (B), kilobytes (K), megabytes (M),
    // gigabytes (G), terabytes (T), and petabytes (P).
    $sz = 'BKMGTP';
    
    // Calculate the appropriate size suffix based on the file size in bytes.
    // The $factor represents the position of the size suffix in the $sz string.    
    $factor = floor((strlen($bytes) - 1) / 3);

    // Calculate the human-readable file size by dividing $bytes by the appropriate power of 1024
    // and formatting the result with the specified number of decimals.
    // The @ symbol is used to suppress any potential warnings if $factor is out of range.
    // For example, if $bytes is very small, $factor might be negative, leading to a warning.
    return sprintf("%.{$decimals}f", $bytes / pow(1024, $factor)) . @$sz[$factor];
}