Resource Leak Detection

Analyze PHP code for resource leak issues.

Detection Patterns

1. Unclosed File Handles

// BUG: File handle not closed
$file = fopen('data.txt', 'r');
$content = fread($file, filesize('data.txt'));
// Missing: fclose($file);

// BUG: Early return without close
$file = fopen($path, 'w');
if (!$valid) {
    return false; // File handle leaked
}
fwrite($file, $data);
fclose($file);

2. Database Connections Not Released

// BUG: Connection not closed
$pdo = new PDO($dsn, $user, $pass);
$stmt = $pdo->query($sql);
// PDO not unset, may hold connection

// BUG: In connection pool context
$connection = $pool->acquire();
$result = $connection->query($sql);
if ($error) {
    throw new Exception(); // Connection leaked
}
$pool->release($connection);

3. Streams Not Freed

// BUG: Stream not closed
$stream = fopen('php://temp', 'r+');
fwrite($stream, $data);
// Missing: fclose($stream);

// BUG: cURL handle not closed
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
// Missing: curl_close($ch);

4. Missing Finally Blocks

// BUG: No finally for cleanup
$lock = $this->acquireLock();
try {
    $this->process();
} catch (Exception $e) {
    $this->log($e);
    throw $e; // Lock not released on exception
}
$this->releaseLock($lock);

// FIXED:
$lock = $this->acquireLock();
try {
    $this->process();
} finally {
    $this->releaseLock($lock);
}

5. Temporary Files Not Cleaned

// BUG: Temp file not deleted
$tempFile = tempnam(sys_get_temp_dir(), 'prefix_');
file_put_contents($tempFile, $data);
$result = $this->processFile($tempFile);
// Missing: unlink($tempFile);

// BUG: Early return leaves temp file
$temp = tmpfile();
if (!$valid) {
    return null; // Temp file not cleaned
}

6. Socket/Network Resources

// BUG: Socket not closed
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_connect($socket, $host, $port);
$data = socket_read($socket, 1024);
// Missing: socket_close($socket);

// BUG: SSH connection not closed
$connection = ssh2_connect($host);
ssh2_auth_password($connection, $user, $pass);
$stream = ssh2_exec($connection, $command);
// Resources not freed

7. Image/GD Resources

// BUG: Image resource not destroyed
$image = imagecreatefromjpeg($path);
$resized = imagescale($image, 100, 100);
imagejpeg($resized, $output);
// Missing: imagedestroy($image); imagedestroy($resized);

8. Doctrine/ORM Resources

// BUG: Large result set in memory
$query = $em->createQuery('SELECT u FROM User u');
$users = $query->getResult(); // All in memory

// BUG: Detached entities not cleared
foreach ($largeDataset as $data) {
    $entity = new Entity($data);
    $em->persist($entity);
    $em->flush();
    // Missing: $em->clear(); for large batches
}

Grep Patterns

# fopen without fclose
Grep: "fopen\([^)]+\)" --glob "**/*.php"
Grep: "fclose\(" --glob "**/*.php"

# curl_init without curl_close
Grep: "curl_init\(" --glob "**/*.php"
Grep: "curl_close\(" --glob "**/*.php"

# try without finally
Grep: "try\s*\{[^}]+\}\s*catch" --glob "**/*.php"

# tempnam/tmpfile usage
Grep: "(tempnam|tmpfile)\(" --glob "**/*.php"

Severity Classification

Pattern	Severity
Database connection leak	🔴 Critical
File handle in loop	🔴 Critical
Lock not released	🔴 Critical
Single file handle	🟠 Major
Temp file not cleaned	🟠 Major
Image resource	🟡 Minor

Best Practices

Use try-finally

$resource = acquire();
try {
    process($resource);
} finally {
    release($resource);
}

Use Context Managers (PHP 8.1+)

// Custom destructor-based cleanup
$file = new FileHandler($path);
// Automatically closed on unset/scope exit

Use Transactions Properly

$connection->beginTransaction();
try {
    $this->process();
    $connection->commit();
} catch (Throwable $e) {
    $connection->rollBack();
    throw $e;
}

Output Format

### Resource Leak: [Description]

**Severity:** 🔴/🟠/🟡
**Location:** `file.php:line`
**Type:** [File Handle|Connection|Stream|Lock|Temp File|...]

**Issue:**
Resource acquired but not properly released.

**Code:**
```php
// Problematic code

Fix:

// With proper cleanup