You can read a group of txt files in a folder and echo the contents like this.
<?php
$directory = "folder/";
$dir = opendir($directory);
$filenames = [];
while (($file = readdir($dir)) !== false) {
$filename = $directory . $file;
$type = filetype($filename);
if($type !== 'file') continue;
$filenames[] = $filename;
}
closedir($dir);
?>