How to use fopen, fwrite and fclose in php for file operations?

In PHP development, file operations are very common. Under normal circumstances, we need to perform file reading, writing, deletion and other operations. Among them, the fopen function and fread function can be used to read the file, and the fopen function, fwrite function and fclose function can be used to write the file. This article will introduce how PHP uses fopen, fwrite and fclose to perform file operations.

1. fopen function

The fopen function is used to open a file. Its syntax is as follows:

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

Among them, $filename represents the file name that needs to be opened, and $mode represents open The mode of the file. $use_include_path indicates whether to search for files in the include path. $context represents the context stream.

The values ​​of $mode are as follows:

mode value	Description
r	Open in read-only mode, the file pointer is located at the head of the file.
r	Open in reading and writing mode, the file pointer is located at the head of the file.
w	Open in writing mode. If the file does not exist, create a new file, otherwise clear the file content. The file pointer is located at the beginning of the file.
w	Open in reading and writing mode. If the file does not exist, create a new file, otherwise clear the file content. The file pointer is located at the beginning of the file.
a	Open in writing mode. If the file does not exist, create a new file. The file pointer is at the end of the file.
a	Open in reading and writing mode. If the file does not exist, create a new file. The file pointer is at the end of the file.
x	Open in write-only mode. If the file does not exist, create a new file, otherwise return false. The file pointer is located at the beginning of the file.
x	Open in reading and writing mode. If the file does not exist, create a new file, otherwise return false. The file pointer is located at the beginning of the file.

Among them, files opened in read-only mode can only be read, not written. A file opened for writing can be written to, but cannot be read, unless the file is closed and reopened.

The following is an example, using the fopen function to open a file:

$fp = fopen('file.txt', 'r');

This code will open a file named file.txt and open it in read-only mode, returning the file stream resource $fp.

2. fwrite function

The fwrite function is used to write data to a file. Its syntax is as follows:

int fwrite(resource $handle, string $string [, int $length ])

Among them, $handle represents the file pointer and $string represents the file to be The string written to the file, $length indicates the length of the data to be written.

If the writing is successful, the number of bytes written will be returned, otherwise false will be returned.

The following is an example of using the fwrite function to write data to an open file:

$fp = fopen('file.txt', 'w');
fwrite($fp, 'hello world');
fclose($fp);

This code will open a file named file.txt and open it in writing mode. Then write the string 'hello world' to the file.

3. fclose function

The fclose function is used to close an opened file. Its syntax is as follows:

bool fclose(resource $handle)

Among them, $handle represents the file pointer.

The following is an example of using the fclose function to close an open file:

$fp = fopen('file.txt', 'a+');
fwrite($fp, 'hello world');
fclose($fp);

This code will open a file named file.txt and open it in read-write mode. Write the string 'hello world' into the file, and finally close the file.

Summary

In PHP development, file operations are very important. The fopen function, fwrite function and fclose function are the three most commonly used functions in file operations. Among them, the fopen function is used to open the file, the fwrite function is used to write data to the file, and the fclose function is used to close the opened file. We can choose different modes for file reading and writing operations according to actual needs.

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