archive.php

<?php

header('Content-type: application/json');
print (new JSONCreator)->getJSON();

class JSONCreator
{
    private $files;

    public function __construct()
    {
        $this->files = [];
    }

    public function getJSON()
    {
        $this->getPDF();
        return json_encode($this->files);
    }

    private function getPDF()
    {
        $iterator = new DirectoryIterator(dirname(__FILE__));
        foreach ($iterator as $fileInfo)
        {
            if ($fileInfo->isDot()) continue;
            if (substr($fileInfo->getFilename(), -4) == '.pdf')
                $this->files[] = [
                    'name' => $fileInfo->getFilename(),
                    'mtime' => $fileInfo->getMTime()
                ];
        }
    }
}