PHP diskfreespace Function
last modified April 3, 2025
The PHP diskfreespace function returns available space on a filesystem
or disk partition. It's useful for monitoring disk usage in applications.
Basic Definition
The diskfreespace function returns the number of available bytes on
the filesystem or disk partition. It's an alias of disk_free_space.
Syntax: diskfreespace(string $directory): float|false. It returns
false on failure. The directory parameter specifies the filesystem to check.
Basic diskfreespace Example
This shows the simplest usage of diskfreespace to check free space.
<?php
declare(strict_types=1);
$freeSpace = diskfreespace("/");
if ($freeSpace !== false) {
echo "Free space: " . $freeSpace . " bytes";
} else {
echo "Could not determine free space";
}
This checks available space on the root partition. The result is in bytes. Always check for false return value in case of errors.
Converting Bytes to Human-Readable Format
Disk space values are often more readable when converted to KB, MB, or GB.
<?php
declare(strict_types=1);
function formatBytes(float $bytes, int $precision = 2): string {
$units = ['B', 'KB', 'MB', 'GB', 'TB'];
$bytes = max($bytes, 0);
$pow = floor(($bytes ? log($bytes) : 0) / log(1024));
$pow = min($pow, count($units) - 1);
$bytes /= (1 << (10 * $pow));
return round($bytes, $precision) . ' ' . $units[$pow];
}
$freeSpace = diskfreespace("/");
if ($freeSpace !== false) {
echo "Free space: " . formatBytes($freeSpace);
} else {
echo "Could not determine free space";
}
The formatBytes helper function converts bytes to appropriate units.
This makes the output more user-friendly for large disk space values.
Checking Multiple Partitions
You can check free space on different partitions or mount points.
<?php
declare(strict_types=1);
$partitions = ["/", "/home", "/var"];
foreach ($partitions as $partition) {
$freeSpace = diskfreespace($partition);
if ($freeSpace !== false) {
echo "Free space on $partition: " .
round($freeSpace / (1024 * 1024)) . " MB\n";
} else {
echo "Could not check space on $partition\n";
}
}
This example checks multiple partitions and displays space in megabytes. Note that the partition must exist and be accessible for the check to succeed.
Calculating Percentage Free Space
Combine with disk_total_space to calculate percentage free space.
<?php
declare(strict_types=1);
$directory = "/";
$free = diskfreespace($directory);
$total = disk_total_space($directory);
if ($free !== false && $total !== false) {
$percentFree = ($free / $total) * 100;
echo "Free space: " . round($percentFree, 2) . "%";
} else {
echo "Could not determine disk space";
}
This calculates the percentage of free space available. Both functions must succeed for the calculation to work. The result shows how full the disk is.
Windows Drive Example
diskfreespace works with Windows drive letters too.
<?php
declare(strict_types=1);
$drive = "C:";
$freeSpace = diskfreespace($drive);
if ($freeSpace !== false) {
$freeGB = $freeSpace / (1024 * 1024 * 1024);
echo "Free space on $drive: " . round($freeGB, 2) . " GB";
} else {
echo "Could not check space on $drive";
}
On Windows, specify the drive letter followed by a colon. The example converts bytes to gigabytes for better readability of typical Windows drive sizes.
Best Practices
- Error Handling: Always check for false return value.
- Permissions: Ensure PHP has access to the filesystem.
- Caching: Don't call frequently as it's filesystem-intensive.
- Cross-platform: Works on both Unix and Windows systems.
- Units: Convert bytes for human-readable output.
Source
PHP diskfreespace Documentation
This tutorial covered the PHP diskfreespace function with practical
examples showing its usage in different scenarios.