Streams and Network Programming

File and file opening modes:

• r,w,a where r represents read, w represents write, a represents append.
• + will make it both read and write.
• In append mode file pointer points to the end which is otherwise at beginning.
• w additionally truncates file size to 0.
• x creates a new file.
• fgetcsv() and fputcsv() vastly simplify the task of accessing CSV files.
• file_get_contents() and file_put_contents() simply file writing.

• if (!file_exist ("filename.txt"))
  {
  throw new Exception ("The file does not exist.");
  }
  
  $file = fopen("filename.txt", "r");
  while (!feof($file))
  {
  $txt .= fread($file, 1);            //Last parameter number of bytes. fgets() stops at newline character.
  fwrite($file, $txt);
  }
  
  fseek($file,10,SEEK_CUR);                  
  //This will move file pointer by itself. The second parameter is the number of bytes to be moved (negative or positive) and third is the location from where to move - SEEK_SET (start), SEEK_CUR (current) and SEEK_END (end).
  
  fclose($file);

   

Directory:

• chdir(“path”) – Changes directory path.
• getcwd() – Gets current working directory.
• mkdir (“path”, 0666, true); – The second parameter gives access mode and last if set to true any missing directories in path will be created. Normally last directory is created.
• is_dir() – Checks if the path is a directory.
• is_executable() – Checks if the path is executable.
• is_file() – Checks if the path exists and is a regular file.
• is_link() – Checks if the path exists and is a symlink.
• is_readable() – Checks if the path exists and is readable.
• is_writable() – Checks if the path exists and is writable.
• is_uploaded_file() – Checks if the path is an uploaded file (sent via HTTP POST).
• File permissions on UNIX systems can be changed by using chmod(), chgrp() and chown() where path and access mode provided.

Network:

• Simple Network Access can be done by using some of the file functions.
• You can create socket servers and clients using the stream functions stream_socket_server() and stream_socket_client().
• Stream filters allow you to pass data in and out of a stream through a series of filters that can alter it dynamically like say filter for compression.