PHP Performance Optimization

Let's dive deep into each optimization technique and understand how they contribute to better performance.

Memory Management and Resource Handling

Memory management in PHP is crucial because poor management can lead to memory leaks and degraded performance. Here's a detailed breakdown:

function processLargeFile($filePath) {
    // Using fopen in 'r' mode for memory efficiency
    $handle = fopen($filePath, 'r');
    if (!$handle) {
        throw new RuntimeException('Failed to open file');
    }

    try {
        while (!feof($handle)) {
            // Using yield instead of storing all lines in memory
            yield fgets($handle);
        }
    } finally {
        // Ensure file handle is always closed, even if an exception occurs
        fclose($handle);
    }
}

// Example of processing a 1GB file with minimal memory usage
function processGiantLogFile($logPath) {
    $stats = ['errors' => 0, 'warnings' => 0];

    foreach (processLargeFile($logPath) as $line) {
        // Process one line at a time instead of loading entire file
        if (strpos($line, 'ERROR') !== false) {
            $stats['errors']++;
        } elseif (strpos($line, 'WARNING') !== false) {
            $stats['warnings']++;
        }

        // Free up memory after processing each line
        unset($line);
    }

    return $stats;
}

Key points about memory management:

• Using generators (yield) prevents loading entire files into memory
• The finally block ensures resources are always freed
• Processing data in chunks reduces memory footprint
• Explicitly unsetting variables when no longer needed helps garbage collection

Smart Data Structures and Caching

Efficient data structures and caching can dramatically improve performance by reducing unnecessary computations and database calls:

class DataProcessor {
    private array $cache = [];
    private int $maxCacheSize;
    private array $cacheTimestamps = [];

    public function __construct(int $maxCacheSize = 1000) {
        $this->maxCacheSize = $maxCacheSize;
    }

    public function processData(string $key, callable $heavyOperation, int $ttl = 3600) {
        // Check if cached data exists and is still valid
        if ($this->isValidCacheEntry($key, $ttl)) {
            return $this->cache[$key];
        }

        $result = $heavyOperation();

        // Implement cache cleanup before adding new items
        $this->maintainCacheSize();

        // Store result with timestamp
        $this->cache[$key] = $result;
        $this->cacheTimestamps[$key] = time();

        return $result;
    }

    private function isValidCacheEntry(string $key, int $ttl): bool {
        if (!isset($this->cache[$key]) || !isset($this->cacheTimestamps[$key])) {
            return false;
        }

        return (time() - $this->cacheTimestamps[$key]) < $ttl;
    }

    private function maintainCacheSize(): void {
        if (count($this->cache) >= $this->maxCacheSize) {
            // Remove oldest entries first (LRU implementation)
            asort($this->cacheTimestamps);
            $oldestKey = array_key_first($this->cacheTimestamps);

            unset($this->cache[$oldestKey]);
            unset($this->cacheTimestamps[$oldestKey]);
        }
    }
}

// Usage example
$processor = new DataProcessor(100);
$result = $processor->processData('expensive_calculation', function() {
    // Simulating expensive operation
    sleep(2);
    return 'expensive result';
}, 1800); // Cache for 30 minutes

This implementation includes:

• Time-based cache expiration (TTL)
• LRU (Least Recently Used) cache eviction strategy
• Memory limit enforcement
• Automatic cache cleanup

String Operations Optimization

String operations in PHP can be memory-intensive. Here's how to optimize them:

class StringOptimizer {
    public function efficientConcatenation(array $strings): string {
        // Use implode instead of concatenation
        return implode('', $strings);
    }

    public function buildLargeHtml(array $data): string {
        // Use output buffering for large string building
        ob_start();

        echo '<div class="container">';
        foreach ($data as $item) {
            printf(
                '<div class="item">%s</div>',
                htmlspecialchars($item, ENT_QUOTES, 'UTF-8')
            );
        }
        echo '</div>';

        return ob_get_clean();
    }

    public function efficientStringReplacement(string $subject, array $replacements): string {
        // Use strtr for multiple replacements instead of str_replace
        return strtr($subject, $replacements);
    }

    public function processLargeText(string $text): string {
        // Precompile regex patterns for better performance
        static $pattern = '/\b\w+@\w+\.\w+\b/';

        return preg_replace_callback(
            $pattern,
            fn($match) => $this->processEmail($match[0]),
            $text
        );
    }
}

// Usage examples
$optimizer = new StringOptimizer();

// Efficient concatenation
$parts = ['Hello', ' ', 'World', '!'];
$result = $optimizer->efficientConcatenation($parts);

// Building large HTML
$data = ['item1', 'item2', 'item3'];
$html = $optimizer->buildLargeHtml($data);

// Efficient string replacement
$replacements = [
    'old' => 'new',
    'bad' => 'good'
];
$text = $optimizer->efficientStringReplacement('old text is bad', $replacements);

Key optimization points:

• Using implode() instead of string concatenation
• Output buffering for building large strings
• Using strtr() for multiple replacements
• Precompiling regex patterns
• Using sprintf() for format strings

Database Query Optimization

Efficient database operations are crucial for application performance:

class DatabaseOptimizer {
    private PDO $pdo;
    private array $queryCache = [];

    public function __construct(PDO $pdo) {
        $this->pdo = $pdo;
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $this->pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
    }

    public function batchInsert(array $records, string $table): void {
        // Build bulk insert query
        $columns = array_keys($records[0]);
        $placeholders = '(' . implode(',', array_fill(0, count($columns), '?')) . ')';
        $values = str_repeat($placeholders . ',', count($records) - 1) . $placeholders;

        $query = sprintf(
            'INSERT INTO %s (%s) VALUES %s',
            $table,
            implode(',', $columns),
            $values
        );

        // Flatten array for bulk insert
        $params = [];
        foreach ($records as $record) {
            foreach ($record as $value) {
                $params[] = $value;
            }
        }

        // Execute bulk insert
        $stmt = $this->pdo->prepare($query);
        $stmt->execute($params);
    }

    public function optimizedSelect(string $table, array $conditions = [], array $fields = ['*']): array {
        $query = sprintf(
            'SELECT %s FROM %s',
            implode(',', $fields),
            $table
        );

        if ($conditions) {
            $where = [];
            $params = [];
            foreach ($conditions as $column => $value) {
                $where[] = "$column = ?";
                $params[] = $value;
            }
            $query .= ' WHERE ' . implode(' AND ', $where);
        }

        // Cache prepared statement
        $cacheKey = md5($query);
        if (!isset($this->queryCache[$cacheKey])) {
            $this->queryCache[$cacheKey] = $this->pdo->prepare($query);
        }

        $stmt = $this->queryCache[$cacheKey];
        $stmt->execute($params ?? []);

        return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
}

// Usage example
$optimizer = new DatabaseOptimizer($pdo);

// Batch insert
$records = [
    ['name' => 'John', 'email' => '[e-mail]'],
    ['name' => 'Jane', 'email' => '[e-mail]']
];
$optimizer->batchInsert($records, 'users');

// Optimized select
$users = $optimizer->optimizedSelect(
    'users',
    ['status' => 'active'],
    ['id', 'name', 'email']
);

Key database optimization techniques:

• Prepared statement caching
• Bulk inserts instead of multiple single inserts
• Selective field retrieval
• Proper indexing (handled at database level)
• Transaction management for batch operations

Array Operations and Loop Optimization

Efficient array handling is crucial for PHP applications:

class ArrayOptimizer {
    public function processArray(array $data, callable $callback): array {
        // Pre-allocate result array
        $result = [];
        $count = count($data);

        // Reserve memory
        $result = array_fill(0, $count, null);

        // Process in chunks for memory efficiency
        foreach (array_chunk($data, 1000) as $chunk) {
            foreach ($chunk as $key => $item) {
                $result[$key] = $callback($item);
            }

            // Free up memory
            unset($chunk);
        }

        return $result;
    }

    public function efficientSearch(array $haystack, $needle): bool {
        // Use isset for array keys
        if (isset($haystack[$needle])) {
            return true;
        }

        // Use in_array with strict comparison
        return in_array($needle, $haystack, true);
    }

    public function arrayIntersectOptimized(array $array1, array $array2): array {
        // Convert second array to hash map for O(1) lookup
        $map = array_flip($array2);

        return array_filter(
            $array1,
            fn($item) => isset($map[$item])
        );
    }
}

// Usage examples
$optimizer = new ArrayOptimizer();

// Process large array
$data = range(1, 10000);
$result = $optimizer->processArray($data, fn($item) => $item * 2);

// Efficient search
$haystack = range(1, 1000);
$found = $optimizer->efficientSearch($haystack, 500);

// Optimized array intersection
$array1 = range(1, 1000);
$array2 = range(500, 1500);
$intersection = $optimizer->arrayIntersectOptimized($array1, $array2);

Key array optimization points:

• Pre-allocating arrays when size is known
• Processing in chunks for memory efficiency
• Using proper array functions (array_key_exists, isset)
• Implementing efficient search algorithms
• Using array_flip for O(1) lookup operations

Error Handling and Logging

Proper error handling and logging is essential for maintaining application stability:

class ErrorHandler {
    private const MAX_LOG_SIZE = 10485760; // 10MB
    private const MAX_LOG_FILES = 5;
    private string $logPath;
    private array $logLevels = [
        'DEBUG' => 0,
        'INFO' => 1,
        'WARNING' => 2,
        'ERROR' => 3,
        'CRITICAL' => 4
    ];

    public function __construct(string $logPath) {
        $this->logPath = $logPath;
    }

    public function handleError(Throwable $e, string $level = 'ERROR'): void {
        // Check log file size
        if (file_exists($this->logPath) && filesize($this->logPath) > self::MAX_LOG_SIZE) {
            $this->rotateLogFile();
        }

        // Format error message
        $message = sprintf(
            "[%s] [%s] %s: %s in %s:%d\nStack trace:\n%s\n",
            date('Y-m-d H:i:s'),
            $level,
            get_class($e),
            $e->getMessage(),
            $e->getFile(),
            $e->getLine(),
            $e->getTraceAsString()
        );

        // Write to log file
        error_log($message, 3, $this->logPath);

        // Handle critical errors
        if ($this->logLevels[$level] >= $this->logLevels['ERROR']) {
            // Notify administrators or monitoring service
            $this->notifyAdministrators($message);
        }
    }

    private function rotateLogFile(): void {
        // Rotate log files
        for ($i = self::MAX_LOG_FILES - 1; $i >= 0; $i--) {
            $oldFile = $this->logPath . ($i > 0 ? '.' . $i : '');
            $newFile = $this->logPath . '.' . ($i + 1);

            if (file_exists($oldFile)) {
                rename($oldFile, $newFile);
            }
        }
    }

    private function notifyAdministrators(string $message): void {
        // Implementation depends on notification system
        // Could be email, Slack, monitoring service, etc.
    }
}

// Usage example
$errorHandler = new ErrorHandler('/var/log/application.log');

try {
    // Some risky operation
    throw new RuntimeException('Something went wrong');
} catch (Throwable $e) {
    $errorHandler->handleError($e, 'ERROR');
}

Key error handling features:

• Log file rotation to manage disk space
• Different log levels for different types of errors
• Stack trace logging for debugging
• Administrator notification for critical errors
• Proper formatting of error messages

Each of these optimizations contributes to creating a robust, performant PHP application. Remember to always measure and profile your application to identify where these optimizations will have the most impact.