How to use file operation functions in php?

PHP is a programming language widely used in web development. It has many file operation functions that can be used to read, write and process files. These functions are very useful because files are a common form of data processing in web development. This article will introduce some commonly used PHP file operation functions and provide some sample code to help you understand better.

1. Open and close files

To use PHP file operation functions, you first need to open the file. The commonly used function is fopen(), which requires two parameters: the file name and the opening mode. The filename is the path to the file you want to open, and the open mode specifies the purpose of the file (read, write, append, etc.). The sample code is as follows:

$handle = fopen('example.txt', 'r');

This code will open the file named example.txt and read its contents. It uses "r" mode, which indicates read-only access to the file. If you want to write or add content at the end of the file, you can use "w" or "a" mode, for example:

$handle = fopen('example.txt', 'w');
$handle = fopen('example.txt', 'a');

After completing the operation on the file, use the fclose() function to close the file handle to ensure that the file Released to other processes or threads. The sample code is as follows:

fclose($handle);

2. Reading and writing files

Once a file is opened, its contents can be read or written using various PHP file operation functions. Below are some of the most commonly used read and write functions.

1. Read the file

(1) The fgets() function can read a line of content in the file and return the line string. The sample code is as follows:

$handle = fopen('example.txt', 'r');
while (!feof($handle)) {
  echo fgets($handle);
}
fclose($handle);

This code will open the file and read the contents line by line until the end of the file is reached. Description: The feof() function determines whether the end of the file has been reached. The fgets() function reads one line from the file at a time and moves from the file pointer to the next line.

(2) The fread() function can read the specified number of bytes and return the read string. The sample code is as follows:

$handle = fopen('example.txt', 'r');
$file_contents = fread($handle, filesize('example.txt'));
fclose($handle);
echo $file_contents;

This code will read the entire file into a string variable and output it to the screen. It should be noted that when using the fread() function to read a file, you must determine how many bytes to read. Here we use the filesize() function to obtain the file size and pass it to fread() to read the entire file.

2. Write to the file

(1) fwrite() function, writes the string to the file. The sample code is as follows:

$handle = fopen('example.txt', 'w');
fwrite($handle, "Hello world!");
fclose($handle);

(2) file_put_contents() function, writes a string to a file. The sample code is as follows:

file_put_contents('example.txt', 'Hello world!');

This code writes Hello world into the example.txt file. Note: If the file does not exist, a new file is created.

3. Other common file operations

1. Check whether the file exists

Use PHP's built-in file_exists() function to check whether the file exists. The sample code is as follows:

if (file_exists('example.txt')) {
  echo '文件存在';
} else {
  echo '文件不存在';
}

2. Copy the file

Use the copy() function to copy the source file to the target file. The sample code is as follows:

if (copy('example.txt', 'example_copy.txt')) {
  echo '文件复制成功';
} else {
  echo '文件复制失败';
}

3. Delete files

Use the unlink() function to delete files. The sample code is as follows:

if (unlink('example.txt')) {
  echo '文件删除成功';
} else {
  echo '文件删除失败';
}

4. Rename the file

Use the rename() function to rename the file. The sample code is as follows:

if (rename('example.txt', 'example_new.txt')) {
  echo '文件重命名成功';
} else {
  echo '文件重命名失败';
}

Summary

PHP file operation functions are the key to many operations in web development, such as reading and writing configuration files, parsing log files, and uploading files, etc. Proficient in these functions can make the operation of files easier and more efficient. This article introduces some PHP file operation functions. For more details, please see the official PHP documentation.

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