How to get closest date compared to an array of dates in PHP

Here Explain about how to find nearest date from any array of dates
Let's say I have an array as follows:

Array
(
    [0] => 2017-09-14
    [1] => 2017-09-15
    [2] => 2017-09-16
    [3] => 2017-09-17
    [4] => 2017-09-18
    [5] => 2017-09-19
)

File Size MB/KB/GB Conversion

The File size conversion as per The size is less than 1 MB, show the size in KB, if it's between 1 MB - 1 GB show it in MB, if it's larger - in GB

<?php
    function fileSizeConversion($bytes)
    {
        if ($bytes >= 1073741824)
        {
            $bytes = number_format($bytes / 1073741824, 2) . ' GB';
        }
        elseif ($bytes >= 1048576)
        {
            $bytes = number_format($bytes / 1048576, 2) . ' MB';
        }
        elseif ($bytes >= 1024)
        {
            $bytes = number_format($bytes / 1024, 2) . ' KB';
        }
        elseif ($bytes > 1)
        {
            $bytes = $bytes . ' bytes';
        }
        elseif ($bytes == 1)
        {
            $bytes = $bytes . ' byte';
        }
        else
        {
            $bytes = '0 bytes';
        }

        return $bytes;
    }

?>