convert gb to bytes php

1function toByteSize($p_sFormatted) {
2    $aUnits = array('B'=>0, 'KB'=>1, 'MB'=>2, 'GB'=>3, 'TB'=>4, 'PB'=>5, 'EB'=>6, 'ZB'=>7, 'YB'=>8);
3    $sUnit = strtoupper(trim(substr($p_sFormatted, -2)));
4    if (intval($sUnit) !== 0) {
5        $sUnit = 'B';
6    }
7    if (!in_array($sUnit, array_keys($aUnits))) {
8        return false;
9    }
10    $iUnits = trim(substr($p_sFormatted, 0, strlen($p_sFormatted) - 2));
11    if (!intval($iUnits) == $iUnits) {
12        return false;
13    }
14    return $iUnits * pow(1024, $aUnits[$sUnit]);
15}

1<?php 
2  function tobytes($size, $type)
3  {
4    $types = array("B", "KB", "MB", "GB", "TB", "PB"); //You can add the rest if needed..
5    
6    if($key = array_search($type, $types))
7      return $size * pow(1024, $key);
8    else return "invalid type";
9  }
10  
11  echo tobytes(15, "MB"); //15728640
12  echo tobytes(2, "KB"); //2048
13  echo tobytes(3, "w/e"); //invalid type 
14?>
15