mysql db wrapper

db.php

<?php

class db {
   /**
    * @var null|array
    */
    protected static $config = null;
    /**
     * @var null|db
     */
    protected static $_inst = NULL;
    
    public static function config ($values) {
        return self::$config = $values;
    }
    /**
     * @static
     * @return null|db
     */
    public static function inst () {
        if (is_null(self::$_inst)) {
            self::$_inst = db::ctor();
        }
        return self::$_inst;
    }
    public static function ctor ($config = null) {
        if (!is_null($config))
            self::config($config);
        return new self(true);
    }
    public static function connect () { return self::inst()->connection(); }
    public static function qry ($sql) { return self::inst()->query($sql); }
    public static function esc ($txt) { return mysql_real_escape_string($txt, db::connect()); }

    protected $connect = null;
    protected $result = null;
    protected $options = array();

    public function __construct ($connect = false)  {
        if ($connect) {
            $this->connection();
        }
    }
    public function __destruct() {
        $this->disconnect();
    }
    public function connection () {
        if (is_null($this->connect)) {
            if (is_null(self::$config)) {
                self::$config = include realpath(dirname(__FILE__) . '/../config') . '/db.dorgen.php';
            } 
            $this->connect   = (self::$config['persistent']) ?
                 mysql_connect (self::$config['host'], self::$config['user'], self::$config['password'], false) :
                 mysql_pconnect(self::$config['host'], self::$config['user'], self::$config['password']);
            if (!$this->connect)
                throw new Exception("Could not connect : " . mysql_error());
            if (!mysql_select_db(self::$config['name']))
                throw new Exception("Could not select database");

        }
        return $this->connect;
    }
    public function disconnect () {
        if ( !is_null($this->connect) ) {
            mysql_close($this->connect);
            $this->connect = null;
        }
    }
    public function query ($sql) {
        if (!($this->result = mysql_query($sql, $this->connection())) || mysql_errno() != 0)
            throw new Exception("sql query \"{$sql}\" failed with message: ".mysql_error());
        return $this;
    }
    public function insert_id () { return mysql_insert_id($this->connect); }
    public function options (array $value) {
        $this->options = $value;
        return $this;
    }
    public function fetch_one (array $options = array()) {
        $row = mysql_fetch_array($this->result, MYSQL_ASSOC);
        $options = array_merge($this->options, $options);
        $this->options = array();
        if (isset($options['expect'])&&$options['expect']) {
            if (!$row) {
                throw new Exception("expected not empty response");
            }
        }
        return $row;
    }
    public function fetch_all (array $options = array()) {
        $rows = array();
        while ( $row = mysql_fetch_array($this->result, MYSQL_ASSOC) ) $rows [] = $row;
        $options = array_merge($this->options, $options);
        $this->options = array();
        if (isset($options['at_least'])) {
            $at_least = $options['at_least'];
            if (count($rows)<$at_least) {
                throw new Exception("expected at least {$at_least} rows");
            }
        }
        return $rows;
    }
    public function begin_transaction () {
        return $this->query("START TRANSACTION");
    }
    public function commit () {
        return $this->query("COMMIT");
    }
    public function rollback () {
        return $this->query("ROLLBACK");
    }

    public static function condition_text ($condition)
    {
        $result = '';
        foreach ($condition as $_field => $_value)
        {
            if ( is_array($_value) )
                $result .= '(' . self::condition_text($_value) . ')';
            elseif ( is_int($_field) && in_array(strtolower($_value), array('and', 'or')) )
                $result .= ' ' . strtoupper($_value) . ' ';
            elseif ( is_string($_field) )
                $result .= '(' . Text::pair($_field, $_value, '=') . ')';
            else
                return false;
        }
        return $result;
    }
}