classe simples de DB

Db.class.php

<?php

class DB {
    /**
     * @var DB
     */
    private static $instancia = NULL;
    
    /**
     * @var Mysql link identifier
     */
    private $dbLink = NULL;
    /**
     * @var string
     */
    private $user = '';
    /**
     * @var string
     */
    private $password = '';
    /**
     * @var string
     */
    private $dbName = '';
    /**
     * @var string
     */
    private $host = '';
    
    /**
     * @var array
     */
    private $lastResult = NULL;
    /**
     * @var string
     */
    private $lastError = '';
    /**
     * @var int
     */
    private $numRows = 0;
    /**
     * @var int
     */
    private $affectedRows = 0;
    /**
     * @var int
     */
    private $lastInsertId = 0;
    
    /**
     * @var int
     */
    private $transacoes = 0;
    /**
     * @var bool
     */
    private $forceRollback = false;
    
    /**
     * @var int
     */
    private $timeInicio = 0;
    /*
     * @var int
     */
    private $timeFim = 0;
    
    /**
     * @param string $host
     * @param string $user
     * @param string $password
     * @param string $dbName
     */
    public function __construct($host, $user, $password, $dbName) {
        $this->host     = $host;
        $this->user     = $user;
        $this->password = $password;
        $this->dbName   = $dbName;
        
        try {
            $this->dbLink = new PDO('mysql:host=' . $this->host . ';dbname=' . $this->dbName, $this->user, $this->password);
        }
        catch (PDOException $e) {
            throw new Exception("Não foi possível conectar ao banco de dados. [" . $e->getCode() . "]");
        }
        
        $this->query('SET NAMES utf8');
        
        self::$instancia = $this;
    }
    
    /**
     * @param string $query
     * @param array $array
     * @param bool $throwError
     * @return int
     */
    public function query($query, $array = array(), $throwError = true) {
        $this->flush();
        
        $this->timeInicio = microtime(true);
        
        $statement = $this->dbLink->prepare($query);
        //$this->result = $statement->execute($array);
        if (!$statement || !$statement->execute($array)) {
            $this->flush();
            $this->error($statement->errorInfo(), $throwError);
        }
        
        if (preg_match('#^ \s* (insert|delete|update|replace) \s #ix', $query)) {
            $this->affectedRows = $statement->rowCount();
            
            if (preg_match("/^\\s*(insert|replace) /i", $query)) {
                $this->lastInsertId = $this->dbLink->lastInsertId();
            }
            $this->timeFimo = microtime();
            return $this->affectedRows;
        } else {
            $this->lastResult = $statement->fetchAll(PDO::FETCH_ASSOC);
            $this->numRows    = count($this->lastResult);
            $this->timeFim    = microtime(true);
            return $this->numRows;
        }
    }
    
    /**
     * @return bool
     */
    public function beginTransaction() {
        if ($this->transacoes == 0) {
            $this->transacoes = $this->transacoes + 1;
            return $this->dbLink->beginTransaction();
        }
        $this->transacoes = $this->transacoes + 1;
        return false;
    }
    
    /**
     * @return bool
     */
    public function commit() {
        if ($this->transacoes == 1) {
            if ($this->forceRollback) {
                return rollback();
            }
            $this->transacoes    = 0;
            $this->forceRollback = false;
            return $this->dbLink->commit();
        }
        $this->transacoes = $this->transacoes - 1;
        return false;
    }
    
    /**
     * @return bool
     */
    public function rollBack() {
        $this->forceRollback = true;
        if ($this->transacoes == 1) {
            $this->transacoes    = 0;
            $this->forceRollback = false;
            return $this->dbLink->rollBack();
        }
        $this->transacoes = $this->transacoes - 1;
        return false;
    }
    
    /**
     *
     */
    private function flush() {
        $this->lastResult = NULL;
        $this->lastError  = NULL;
        
        $this->numRows      = 0;
        $this->affectedRows = 0;
        $this->lastInsertId = 0;
        
        $this->timeInicio = 0;
        $this->timeFim    = 0;
        
        $this->lastError = '';
    }
    
    /**
     * @param array $errorInfo
     * @param bool $throwError
     */
    private function error($errorInfo, $throwError = true) {
        $this->lastError = $errorInfo[1] . ": " . $errorInfo[2];
        if ($throwError)
            throw new Exception($this->lastError);
    }
    
    /**
     * @return DB
     */
    public static function getInstancia() {
        return self::$instancia;
    }
    
    /**
     * @return int
     */
    public function getAffectedRows() {
        return $this->affectedRows;
    }
    
    /**
     * @return Mysql
     */
    public function getDbLink() {
        return $this->dbLink;
    }
    
    /**
     * @return string
     */
    public function getDbName() {
        return $this->dbName;
    }
    
    /**
     * @return string
     */
    public function getHost() {
        return $this->host;
    }
    
    /**
     * @return string
     */
    public function getLastError() {
        return $this->lastError;
    }
    
    /**
     * @return int
     */
    public function getLastInsertId() {
        return $this->lastInsertId;
    }
    
    /**
     * @return array
     */
    public function getLastResult() {
        return $this->lastResult;
    }
    
    /**
     * @return int
     */
    public function getNumRows() {
        return $this->numRows;
    }
    
    /**
     * @return string
     */
    public function getPassword() {
        return $this->password;
    }
    
    /**
     * @return string
     */
    public function getUser() {
        return $this->user;
    }
    
    /**
     * @return int
     */
    public function getQueryExecTime() {
        return $this->timeFim - $this->timeInicio;
    }
}

?>