Mastering PHP fileperms(): Retrieve and Interpret File Permissions

In PHP development, you may need to obtain a file's permission information, such as checking whether it is readable, writable, or executable. The PHP function fileperms() helps achieve this. This article introduces the usage and examples of fileperms().

The fileperms() function retrieves a file's permissions. Its prototype is: string fileperms ( string $filename ) Here $filename is the path of the file whose permissions you want to get. The function returns a string representing the file's permissions.

Example of using fileperms() to get a file's permissions:

<?php
$filename = 'test.txt';
$perms = fileperms($filename);
echo "文件{$filename}的权限是：{$perms}";
?>

Running this code might output something like: 文件test.txt的权限是：33204 The returned integer encodes the permission bits; the lower nine bits indicate read, write, and execute permissions. To convert this integer into a human‑readable permission string, you can use a helper function:

<?php
function format_perms($perms) {
    $result = '';
    if (($perms & 0xC000) == 0xC000) { $result .= 's'; }
    elseif (($perms & 0xA000) == 0xA000) { $result .= 'l'; }
    elseif (($perms & 0x8000) == 0x8000) { $result .= '-'; }
    elseif (($perms & 0x6000) == 0x6000) { $result .= 'b'; }
    elseif (($perms & 0x4000) == 0x4000) { $result .= 'd'; }
    elseif (($perms & 0x2000) == 0x2000) { $result .= 'c'; }
    elseif (($perms & 0x1000) == 0x1000) { $result .= 'p'; }
    else { $result .= 'u'; }

    if (($perms & 0x0100) == 0x0100) { $result .= 'r'; } else { $result .= '-'; }
    if (($perms & 0x0080) == 0x0080) { $result .= 'w'; } else { $result .= '-'; }

    if (($perms & 0x0040) == 0x0040) {
        if ($perms & 0x0800) { $result .= 's'; } else { $result .= 'x'; }
    } else {
        if ($perms & 0x0800) { $result .= 'S'; } else { $result .= '-'; }
    }

    if (($perms & 0x0008) == 0x0008) {
        if ($perms & 0x0400) { $result .= 't'; } else { $result .= 'x'; }
    } else {
        if ($perms & 0x0400) { $result .= 'T'; } else { $result .= '-'; }
    }

    if (($perms & 0x0004) == 0x0004) { $result .= 'r'; } else { $result .= '-'; }
    if (($perms & 0x0002) == 0x0002) { $result .= 'w'; } else { $result .= '-'; }
    if (($perms & 0x0001) == 0x0001) { $result .= 'x'; } else { $result .= '-'; }

    return $result;
}
$filename = 'test.txt';
$perms = fileperms($filename);
$formatted_perms = format_perms($perms);
echo "文件{$filename}的权限是：{$formatted_perms}";
?>

Running this code may produce an output such as:

文件test.txt的权限是：-rw-r--r--

Summary

In PHP development, the fileperms() function allows you to easily retrieve a file's permission bits; by applying bitwise operations or a helper format_perms() function, you can convert the integer into a readable permission string, ensuring your file operations respect the required permissions.