Detailed explanation of file operation function PHP fopen()

In PHP, it is often necessary to read and write files, and the most basic function among the file operation functions is fopen(), which can open a file and return the handle of the file. Subsequent operations need to be performed through this handle.

Syntax format
fopen(file, mode, use_include_path, context)

Parameter explanation
file: required parameter, the path and name of the open file.
mode: required parameter, the mode for opening the file, which can be one or more of the following modes
r: read-only mode, the file pointer points to the file header.
r: Read and write mode, the file pointer points to the file header.
w: Write-only mode, overwrite the file if it exists, create the file if it does not exist.
w: Read and write mode, overwrite the file if it exists, create the file if it does not exist.
a: Write-only append mode, the file pointer points to the end of the file, and the file is created if it does not exist.
a: Read-write append mode, the file pointer points to the end of the file, if the file does not exist, the file is created.
x: Create a new file in write-only mode. If the file exists, return false and do not create it.
x: Create a new file and read and write mode. If the file exists, it returns false and does not create it.
b: Open binary files, which can be used in combination with the above modes.
t: Open a text file and can be used in combination with the above modes.
use_include_path: Optional parameter, if set to TRUE, the function will find files in include_path.
context: Optional parameter, an optional parameter that can contain stream data pointing to a context identifier.

The code to open a file can take the following form:

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

After opening the file, we can use fread() and fwrite() to read and write the file, for example:

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

// 读取文件中的一行
echo fgets($handle);

// 关闭文件
fclose($handle);

In the above code, we use the fgets() function to read a line in the file, and then use the fclose() function to close the open file.

If an error occurs during reading and writing, you can use the feof() function to detect the end of the file:

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

// 当文件结束时停止读取
while (!feof($handle)) {
    echo fgets($handle);
}

// 关闭文件
fclose($handle);

To summarize, the fopen() function is the most basic function in PHP file reading and writing. Through different parameters, we can set the opening mode of the file, and then perform read and write operations on the file. After the operation is completed, we must close the file through the fclose() function, which is a good programming habit.

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