How to Use PHP’s is_writable() to Check File and Directory Permissions

is_writable() function syntax

bool is_writable ( string $filename )

The $filename parameter is the path of the file or directory to be checked.

Usage of is_writable()

Check if a file is writable

The is_writable() function returns true if the specified file exists and is writable, otherwise false. Example:

$filename = 'example.txt';
if (is_writable($filename)) {
    echo '文件可写';
} else {
    echo '文件不可写';
}

Check if a directory is writable

The same function can verify directory writability. Example:

$directory = 'example';
if (is_writable($directory)) {
    echo '目录可写';
} else {
    echo '目录不可写';
}

Check if a file exists and is writable

Combine file_exists() with is_writable() to first ensure the file exists, then test writability. Example:

$filename = 'example.txt';
if (file_exists($filename)) {
    if (is_writable($filename)) {
        echo '文件存在且可写';
    } else {
        echo '文件存在但不可写';
    }
} else {
    echo '文件不存在';
}

Check write permission of a file or directory

The function also indicates whether the target has write permission. Example:

$filename = 'example.txt';
if (is_writable($filename)) {
    echo '文件或目录具有可写的权限';
} else {
    echo '文件或目录不具有可写的权限';
}

Summary

The is_writable() function is a useful tool for determining whether a file or directory is writable. By passing the path to the target, developers can quickly assess write permissions and handle file system operations accordingly.