How can I check if a file exists on a remote server using PHP?

Question

How can I check if a specific file exists on a remote server using PHP via FTP connections?

Answer 1

This is an optimization of @JohanPretorius solution, and an answer for comments about "slow and inefficient for large dirs" of @Andrew and other: if you need more than one "file_exist checking", this function is a optimal solution.

ftp_file_exists() caching last folder

  function ftp_file_exists(
      $file, // the file that you looking for
      $path = "SERVER_FOLDER",   // the remote folder where it is
      $ftp_server = "ftp.example.com", //Server to connect to
      $ftp_user = "ftpserver_username", //Server username
      $ftp_pwd = "ftpserver_password", //Server password
      $useCache = 1  // ALERT: do not $useCache when changing the remote folder $path.
  ){

      static $cache_ftp_nlist = array();
      static $cache_signature = '';

      $new_signature = "$ftp_server/$path";

      if(!$useCache || $new_signature!=$cache_signature) 
          {
              $useCache = 0;
              //$new_signature = $cache_signature;
              $cache_signature = $new_signature;
               // setup the connection
               $conn_id         = ftp_connect($ftp_server) or die("Error connecting $ftp_server");
               $ftp_login           = ftp_login($conn_id, $ftp_user, $ftp_pwd);
               $cache_ftp_nlist = ftp_nlist($conn_id, $path);

               if ($cache_ftp_nlist===FALSE)die("erro no ftp_nlist");
          }

        //$check_file_exist = "$path/$file";
        $check_file_exist = "$file";

        if(in_array($check_file_exist, $cache_ftp_nlist)) 
            {
                echo "Found: ".$check_file_exist." in folder: ".$path;
            } 
        else 
            {
                echo "Not Found: ".$check_file_exist." in folder: ".$path;  
            };
        // use for debuging: var_dump($cache_ftp_nlist);
        if(!$useCache) ftp_close($conn_id);
    } //function end

    //Output messages
    echo ftp_file_exists("file1-to-find.ext"); // do FTP
    echo ftp_file_exists("file2-to-find.ext"); // using cache
    echo ftp_file_exists("file3-to-find.ext"); // using cache
    echo ftp_file_exists("file-to-find.ext","OTHER_FOLDER"); // do FTP