PHP中的fopen函数有什么作用
PHP中的fopen函数用于打开一个文件或URL,其语法是【fopen(filename,mode,include_path,context)】,参数【mode】表示请求到该文件流的访问类型。
PHP fopen函数有什么用?
定义和用法
fopen() 函数打开一个文件或 URL。
如果 fopen() 失败,它将返回 FALSE 并附带错误信息。您可以通过在函数名前面添加一个 '@' 来隐藏错误输出。
语法
fopen(filename,mode,include_path,context)
参数
filename 必需。规定要打开的文件或 URL。
mode 必需。规定您请求到该文件/流的访问类型。
可能的值:
"r" (只读方式打开,将文件指针指向文件头)
"r+" (读写方式打开,将文件指针指向文件头)
"w" (写入方式打开,清除文件内容,如果文件不存在则尝试创建之)
"w+" (读写方式打开,清除文件内容,如果文件不存在则尝试创建之)
"a" (写入方式打开,将文件指针指向文件末尾进行写入,如果文件不存在则尝试创建之)
"a+" (读写方式打开,通过将文件指针指向文件末尾进行写入来保存文件内容)
"x" (创建一个新的文件并以写入方式打开,如果文件已存在则返回 FALSE 和一个错误)
"x+" (创建一个新的文件并以读写方式打开,如果文件已存在则返回 FALSE 和一个错误)
include_path 可选。如果您还想在 include_path(在 php.ini 中)中搜索文件的话,请设置该参数为 '1'。
context 可选。规定文件句柄的环境。context 是一套可以修改流的行为的选项。
提示和注释
注释:当书写一个文本文件时,请确保您使用了正确的行结束符!在 Unix 系统中,行结束符为 \n;在 Windows 系统中,行结束符为 \r\n;在 Macintosh 系统中,行结束符为 \r。Windows 系统中提供了一个文本转换标记 "t" ,可以透明地将 \n 转换为 \r\n。您还可以使用 "b" 来强制使用二进制模式,这样就不会转换数据。为了使用这些标记,请使用 "b" 或者 "t" 来作为 mode 参数的最后一个字符。
实例
<?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:password@example.com/test.txt","w"); ?>
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