fopen(filename,mode,include_path,context)

Possible values:
可用值：

• "r" (Read only. Starts at the beginning of the file)
  “r”（只读格式。始于文件的开头）
• "r+" (Read/Write. Starts at the beginning of the file)
  “r+”（可读/可写。始于文件的开头）
• "w" (Write only. Opens and clears the contents of file; or creates a new file if it doesn't exist)
  “w”（只写格式。打开或清除文件的内容；或者创建一个不存在的文件）
• "w+" (Read/Write. Opens and clears the contents of file; or creates a new file if it doesn't exist)
  “w+”（可读/可写。打开或清除文件的内容；或创建一个不存在的新文件）
• "a" (Write only. Opens and writes to the end of the file or creates a new file if it doesn't exist)
  “a”（只写格式。打开文件，并在文件的末尾处书写内容；或创建一个新的文件）
• "a+" (Read/Write. Preserves file content by writing to the end of the file)
  “a+”（可读/可写。通过在文件的末尾书写内容来保存文件的内容）
• "x" (Write only. Creates a new file. Returns FALSE and an error if file already exists)
  “x”（只写格式。创建一个新的文件）
• "x+" (Read/Write. Creates a new file. Returns FALSE and an error if file already exists)
  “x+”（可读/可写。创建一个新的文件。如果文件已经存在，则返回False或产生一个错误）

<?php
$file = fopen("test.txt","r");
$file = fopen("/home/test/test.txt","r");
$file = fopen("/home/test/test.gif","wb");
$file = fopen("http://www.example.com/","r");
$file = fopen("ftp://user:[email protected]/test.txt","w");
?>