PHP umask Function
last modified April 3, 2025
The PHP umask function sets the default permission mask for files
and directories. It affects permissions of newly created files and directories.
Basic Definition
The umask function changes the current umask (user mask) value.
It takes an octal value representing permissions to be disabled by default.
Syntax: umask(?int $mask = null): int. The function returns the
previous umask value. Without parameters, it returns current umask without
changing it.
Basic umask Example
This shows how to set a basic umask and check its effect on file creation.
<?php
declare(strict_types=1);
$old_mask = umask(0);
echo "Old umask: " . decoct($old_mask) . "\n";
$file = fopen("test.txt", "w");
fclose($file);
$perms = fileperms("test.txt");
echo "File permissions: " . decoct($perms & 0777) . "\n";
umask($old_mask); // Restore original umask
unlink("test.txt");
This sets umask to 0, allowing full permissions (777). The created file will have permissions based on the umask. We restore the original umask afterward.
Restrictive umask Example
This demonstrates how a restrictive umask affects new file permissions.
<?php
declare(strict_types=1);
$old_mask = umask(0077); // Remove all group/other permissions
echo "Old umask: " . decoct($old_mask) . "\n";
$file = fopen("secure.txt", "w");
fclose($file);
$perms = fileperms("secure.txt");
echo "File permissions: " . decoct($perms & 0777) . "\n";
umask($old_mask); // Restore original umask
unlink("secure.txt");
With umask 0077, new files will have permissions 600 (rw-------). The umask value is subtracted from the default permissions (666 for files).
Directory Creation with umask
This example shows how umask affects directory permissions differently.
<?php
declare(strict_types=1);
$old_mask = umask(0022); // Common default umask
echo "Old umask: " . decoct($old_mask) . "\n";
mkdir("new_directory");
$perms = fileperms("new_directory");
echo "Directory permissions: " . decoct($perms & 0777) . "\n";
umask($old_mask); // Restore original umask
rmdir("new_directory");
With umask 0022, new directories will have permissions 755 (rwxr-xr-x). The umask subtracts from default directory permissions (777). Execute bits remain.
Temporary umask Change
This shows how to temporarily change umask for specific operations.
<?php
declare(strict_types=1);
function createSecureFile(string $filename): void {
$old_mask = umask(0077);
$file = fopen($filename, "w");
fclose($file);
umask($old_mask);
}
createSecureFile("private.txt");
$perms = fileperms("private.txt");
echo "File permissions: " . decoct($perms & 0777) . "\n";
unlink("private.txt");
The function temporarily sets a restrictive umask for file creation. The umask is automatically restored after file creation, preventing global side effects.
Checking Current umask
This example demonstrates how to check the current umask without changing it.
<?php
declare(strict_types=1);
$current_umask = umask();
echo "Current umask: " . decoct($current_umask) . "\n";
// Create a test file to see actual permissions
$file = fopen("testfile.txt", "w");
fclose($file);
$perms = fileperms("testfile.txt");
echo "Actual file permissions: " . decoct($perms & 0777) . "\n";
unlink("testfile.txt");
Calling umask() without parameters returns the current umask value. The actual file permissions will be 666 minus the umask value (for files).
Best Practices
- Restore umask: Always restore original umask after changes.
- Octal notation: Use octal numbers (e.g., 077) for clarity.
- Scope: Limit umask changes to smallest necessary scope.
- Security: Consider security implications of permissions.
- Document: Document umask changes in team environments.
Source
This tutorial covered the PHP umask function with practical
examples showing its usage for permission control in filesystem operations.