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PHP file handling - open/close files

黄舟

Release： 2023-03-07 13:16:01

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PHP File Processing - Open/Close File

What is file processing?

File processing includes reading, closing, rewriting, etc. Mastering file processing requires readers to clarify their thinking and master the key steps and common functions of file processing, so that they can use it freely!

For example, accessing a file requires 3 steps: opening the file, reading and writing the file, and closing the file. Other operations on files are either included in reading and writing files (such as displaying content, writing content, etc.), or are related to the attributes of the file itself (such as file traversal, file renaming, etc.). So starting from this article, we will give a detailed introduction to commonly used file processing technologies.

In today’s article, we will first introduce Opening/closing files. To open and close files, use the fopen() function and fclose() function. You should be extremely careful when opening files, because you may delete all the contents of the file if you are not careful.

1: Open the file

When operating a file, the first thing we have to do is open the file. This is The first step in data access. Use the fopen() function to open a file in PHP. The syntax of the fopen() function is as follows:

resource fopen ( string $filename , string $mode [, bool $use_include_path = false [, resource $context ]] )

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The parameter filename is the file name containing the path to be opened, which can be a relative path or an absolute path. If there is no prefix on the side, it means that the local file is being opened. The parameter mode is the way to open the file. The possible values are as follows:

mode	Mode name	Description
r	Read only	Read mode—read, the file pointer is at the beginning of the file
r+	Read and write	Read and write mode—read For reading and writing, the file pointer is at the beginning of the file. Writing before the end of the contents of an existing file will overwrite the original
W	Write only	Write mode—write Enter the file, and the file pointer points to the header file. If the file exists, all file contents are deleted, otherwise the function will create the file
w+	Read and write	Read and write mode—for reading When writing, the file pointer points to the header file. If the file exists, all file contents are deleted, otherwise the function will create the file
x	Write with caution	Open the file in write mode, from the file Start writing. If the file already exists, the file will not be opened, the function returns false, and PHP will generate a warning
x+	Write with caution	Open the file in read/write mode and start writing from the beginning of the file. If the file already exists, the file will not be opened, the function returns false, and PHP will generate a warning
a	Append	Append mode Open the file, and the file pointer points to the tail file. If the file already has content, it will be appended from the end of the file. If the file does not exist, the function will create the file
a+	Append	Open the file in append mode, and the file pointer points to the header file. If the file already has content, it will be appended or read from the end of the file. If the file does not exist, the function will Create this file
b	binary	Binary mode - used to connect with other modes. This may be used if the file system can differentiate between binary files and text files. Windows can differentiate; UNIX does not. This option is recommended for maximum portability. It is the default mode
t	text	used in combination with other modes. This mode is only an option under Windows

第三个参数 use_include_path 是可选的，该参数在配置文件 php.ini 中指定一个路径，如F:\AppServ\www\mess.php，如果希望服务器在这个路径下打开所指定的文件，可以将其值上设置为 1 或者 true。

二：关闭文件

对文件的操作结束后应该关闭这个文件，否则可能会引起错误。在 PHP 中使用 fclose()函数关闭文件，该函数的语法格式如下;

bool fclose ( resource $handle )

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该函数将参数 handle 指向的文件关闭，如果成功，那么返回true，否则返回false。其中的文件指针必须是有效的，并且是通过 fopen()函数成功打开的文件。

具体我们看下下面的示例代码：

<?php
header("Content-Type:text/html; charset=utf-8");
$f_open = fopen("../file.txt","rb"); // 打开文件
.................                      //这里是对文件进行操作
fclose($f_open)                       //操作完成后关闭文件
?>

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打开/关闭文件就介绍到这里，下一篇我们介绍《PHP文件处理—读取文件(一个字符,字串)》！

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