Snippets subida ficheros. Obtener extensión fichero y cambiar nombre fichero

get_file_extension.php

<?php
function get_file_extension($file_name = '') {
    $file_name = (empty($file_name)) ? 'bla.bla..pdf' : $file_name;
    
    preg_match('/[^\.]+$/i', $file_name, $ext);
    return $ext[0];
}
?>

index.php

<?php
var_dump(merge_file_extension());
?>

merge_file_extension.php

<?php
function merge_file_extension($file_name = '', $extension = '', $addon_type = '') {
    $file_name = (empty($file_name)) ? 'bla.bla..pdf' : $file_name;
    $extension = (empty($extension)) ? get_file_extension($filename) : $extension;
    
    switch(trim($addon_type)) {
      case 'datetime':
      $filename_addon = date('YmdHis');
      break;
      
      case 'microtime':
      $filename_addon = microtime();
      break;
      
      default:
      $filename_addon = time();
      break;
    }
    
    $file_name = substr(strtolower($file_name), 0, -(strlen($ext)+1)).'-'.$filename_addon.'.'.$ext;
    
    return $file_name;
}
?>