PHP Data Acces Object

<?php 
class db {
	
	const HOSTNAME = 'localhost';
	const DATABASE = 'hostname';
	const PASSWORD = 'password';
	const USER = 'user';
	
	private static $instance = false;
	
	public $oMysqli = false;
	private $arResult;
	
	
	public static $queryLog;
	public static $log = true;
	

	/**
	 * Connects to database if there is no connection;
	 * @param bool $autocommit
	 * @todo implement autocommit
	 * @throws Exception
	 */
	
	private function __construct(  ){
		
		
		if(!$this->oMysqli){
			$this->oMysqli = new mysqli(db::HOSTNAME,db::USER, db::PASSWORD, db::DATABASE);				
			if(mysqli_connect_errno())			
				throw new Exception('Cannot connect to database: '.$this->oMysqli->error);
			
		}
	}
	
	/**
	 * Creates instance if there is none
	 * @return $instance
	 */
	public function get(  ){		
		if(!self::$instance)
			self::$instance = new self();
		
		return self::$instance;		
	}	
	
	/**
	 * Returns the total query time
	 */
	public static function getTotalQueryTime(){
		$total = 0;
		foreach	(self::$queryLog as $key => $log){
			if($key == 'exectime'){
				$total += (int) $log;
			}
		}
		return $total;
	}
	

	
	/**
	 * Performs a database query
	 * @throws Exception
	 */
	public function query( $query ){		
		$starttime = $this->timeToFloat ();
		$this->arResult = $this->oMysqli->query($query);			
		$endtime = $this->timeToFloat ();
		$exectime = ($endtime - $starttime);	
		if(self::$log){
			self::$queryLog[] = array (
					'query' => $query,
					'exectime' => $exectime,
					'affected_rows' => $this->oMysqli->affected_rows,
					'last_insert_id' => $this->oMysqli->insert_id );
		}
	
		return $this;	
	}
	/**
	 * Returns the query result
	 * @param boolean $objects
	 */
	public function allAssoc( $objects = false ){
		$arAssoc = array();

		while($result = $this->arResult->fetch_assoc()){
			
			if($objects){
				$oRes = new stdClass();
				
				foreach($result as $key => $value)
					$oRes->$key = $value;
			
				$arAssoc[] = $oRes;
				
			} else 
				$arAssoc[] = $result;
		}
		
		return $arAssoc;
	}	
	
	public function __get($name){
		return $this->oMysqli->$name;		
	}
	
	/**
	 * Magic method to inherit 
	 * all mysqli's functionalities
	 * @param string $name
	 * @param string/array $args
	 */
	public function __call($name , $args ){				
		if(sizeof($args) == 1)
			$args = array_shift($args);
		return $this->oMysqli->$name($args);				
	}
	
	/**
	 * returns time as a float
	 */
	
	private function timeToFloat() {
	
		$time = microtime ();
		$time = explode ( " ", $time );
		$time = $time [1] + $time [0];
		return $time;
	
	}
	/**
	 * List of reserved mysql words
	 * used by the query builder to put
	 * backticks around m if they occur
	 */
	public static $reservedMysqlWords = array (
			'accessible',
			'add',
			'all',
			'alter',
			'analyze',
			'and',
			'as',
			'asc',
			'asensitive',
			'before',
			'between',
			'bigint',
			'binary',
			'blob',
			'both',
			'by',
			'call',
			'cascade',
			'case',
			'change',
			'char',
			'character',
			'check',
			'collate',
			'column',
			'condition',
			'connection',
			'constraint',
			'continue',
			'convert',
			'create',
			'cross',
			'current_date',
			'current_time',
			'current_timestamp',
			'current_user',
			'cursor',
			'database',
			'databases',
			'day_hour',
			'day_microsecond',
			'day_minute',
			'day_second',
			'dec',
			'decimal',
			'declare',
			'default',
			'delayed',
			'delete',
			'desc',
			'describe',
			'deterministic',
			'distinct',
			'distinctrow',
			'div',
			'double',
			'drop',
			'dual',
			'each',
			'else',
			'elseif',
			'enclosed',
			'escaped',
			'exists',
			'exit',
			'explain',
			'false',
			'fetch',
			'float',
			'float4',
			'float8',
			'for',
			'force',
			'foreign',
			'from',
			'fulltext',
			'goto',
			'grant',
			'group',
			'having',
			'high_priority',
			'hour_microsecond',
			'hour_minute',
			'hour_second',
			'if',
			'ignore',
			'in',
			'index',
			'infile',
			'inner',
			'inout',
			'insensitive',
			'insert',
			'int',
			'int1',
			'int2',
			'int3',
			'int4',
			'int8',
			'integer',
			'interval',
			'into',
			'is',
			'iterate',
			'join',
			'key',
			'keys',
			'kill',
			'label',
			'leading',
			'leave',
			'left',
			'like',
			'limit',
			'linear',
			'lines',
			'load',
			'localtime',
			'localtimestamp',
			'lock',
			'long',
			'longblob',
			'longtext',
			'loop',
			'low_priority',
			'master_ssl_verify_server_cert',
			'match',
			'mediumblob',
			'mediumint',
			'mediumtext',
			'middleint',
			'minute_microsecond',
			'minute_second',
			'mod',
			'modifies',
			'natural',
			'no_write_to_binlog',
			'not',
			'null',
			'number',
			'numeric',
			'on',
			'optimize',
			'option',
			'optionally',
			'or',
			'order',
			'out',
			'outer',
			'outfile',
			'precision',
			'primary',
			'procedure',
			'purge',
			'range',
			'read',
			'read_only',
			'read_write',
			'reads',
			'real',
			'references',
			'regexp',
			'release',
			'rename',
			'repeat',
			'replace',
			'require',
			'reserved',
			'restrict',
			'return',
			'revoke',
			'right',
			'rlike',
			'schema',
			'schemas',
			'second_microsecond',
			'select',
			'sensitive',
			'separator',
			'set',
			'show',
			'smallint',
			'spatial',
			'specific',
			'sql',
			'sql_big_result',
			'sql_calc_found_rows',
			'sql_small_result',
			'sqlexception',
			'sqlstate',
			'sqlwarning',
			'ssl',
			'starting',
			'straight_join',
			'table',
			'terminated',
			'then',
			'tinyblob',
			'tinyint',
			'tinytext',
			'to',
			'trailing',
			'trigger',
			'true',
			'undo',
			'union',
			'unique',
			'unlock',
			'unsigned',
			'update',
			'upgrade',
			'usage',
			'use',
			'using',
			'utc_date',
			'utc_time',
			'utc_timestamp',
			'values',
			'varbinary',
			'varchar',
			'varcharacter',
			'varying',
			'when',
			'where',
			'while',
			'with',
			'write',
			'xor',
			'year_month',
			'zerofill',
			'__class__',
			'__compiler_halt_offset__',
			'__dir__',
			'__file__',
			'__function__',
			'__method__',
			'__namespace__',
			'abday_1',
			'abday_2',
			'abday_3',
			'abday_4',
			'abday_5',
			'abday_6',
			'abday_7',
			'abmon_1',
			'abmon_10',
			'abmon_11',
			'abmon_12',
			'abmon_2',
			'abmon_3',
			'abmon_4',
			'abmon_5',
			'abmon_6',
			'abmon_7',
			'abmon_8',
			'abmon_9',
			'abstract',
			'alt_digits',
			'am_str',
			'array',
			'assert_active',
			'assert_bail',
			'assert_callback',
			'assert_quiet_eval',
			'assert_warning',
			'break',
			'case_lower',
			'case_upper',
			'catch',
			'cfunction',
			'char_max',
			'class',
			'clone',
			'codeset',
			'connection_aborted',
			'connection_normal',
			'connection_timeout',
			'const',
			'count_normal',
			'count_recursive',
			'credits_all',
			'credits_docs',
			'credits_fullpage',
			'credits_general',
			'credits_group',
			'credits_modules',
			'credits_qa',
			'credits_sapi',
			'crncystr',
			'crypt_blowfish',
			'crypt_ext_des',
			'crypt_md5',
			'crypt_salt_length',
			'crypt_std_des',
			'currency_symbol',
			'd_fmt',
			'd_t_fmt',
			'day_1',
			'day_2',
			'day_3',
			'day_4',
			'day_5',
			'day_6',
			'day_7',
			'decimal_point',
			'default_include_path',
			'die',
			'directory_separator',
			'do',
			'e_all',
			'e_compile_error',
			'e_compile_warning',
			'e_core_error',
			'e_core_warning',
			'e_deprecated',
			'e_error',
			'e_notice',
			'e_parse',
			'e_strict',
			'e_user_deprecated',
			'e_user_error',
			'e_user_notice',
			'e_user_warning',
			'e_warning',
			'echo',
			'empty',
			'enddeclare',
			'endfor',
			'endforeach',
			'endif',
			'endswitch',
			'endwhile',
			'ent_compat',
			'ent_noquotes',
			'ent_quotes',
			'era',
			'era_d_fmt',
			'era_d_t_fmt',
			'era_t_fmt',
			'era_year',
			'eval',
			'extends',
			'extr_if_exists',
			'extr_overwrite',
			'extr_prefix_all',
			'extr_prefix_if_exists',
			'extr_prefix_invalid',
			'extr_prefix_same',
			'extr_skip',
			'final',
			'foreach',
			'frac_digits',
			'function',
			'global',
			'grouping',
			'html_entities',
			'html_specialchars',
			'implements',
			'include',
			'include_once',
			'info_all',
			'info_configuration',
			'info_credits',
			'info_environment',
			'info_general',
			'info_license',
			'info_modules',
			'info_variables',
			'ini_all',
			'ini_perdir',
			'ini_system',
			'ini_user',
			'instanceof',
			'int_curr_symbol',
			'int_frac_digits',
			'interface',
			'isset',
			'lc_all',
			'lc_collate',
			'lc_ctype',
			'lc_messages',
			'lc_monetary',
			'lc_numeric',
			'lc_time',
			'list',
			'lock_ex',
			'lock_nb',
			'lock_sh',
			'lock_un',
			'log_alert',
			'log_auth',
			'log_authpriv',
			'log_cons',
			'log_crit',
			'log_cron',
			'log_daemon',
			'log_debug',
			'log_emerg',
			'log_err',
			'log_info',
			'log_kern',
			'log_local0',
			'log_local1',
			'log_local2',
			'log_local3',
			'log_local4',
			'log_local5',
			'log_local6',
			'log_local7',
			'log_lpr',
			'log_mail',
			'log_ndelay',
			'log_news',
			'log_notice',
			'log_nowait',
			'log_odelay',
			'log_perror',
			'log_pid',
			'log_syslog',
			'log_user',
			'log_uucp',
			'log_warning',
			'm_1_pi',
			'm_2_pi',
			'm_2_sqrtpi',
			'm_e',
			'm_ln10',
			'm_ln2',
			'm_log10e',
			'm_log2e',
			'm_pi',
			'm_pi_2',
			'm_pi_4',
			'm_sqrt1_2',
			'm_sqrt2',
			'mon_1',
			'mon_10',
			'mon_11',
			'mon_12',
			'mon_2',
			'mon_3',
			'mon_4',
			'mon_5',
			'mon_6',
			'mon_7',
			'mon_8',
			'mon_9',
			'mon_decimal_point',
			'mon_grouping',
			'mon_thousands_sep',
			'n_cs_precedes',
			'n_sep_by_space',
			'n_sign_posn',
			'namespace',
			'negative_sign',
			'new',
			'noexpr',
			'nostr',
			'old_function',
			'p_cs_precedes',
			'p_sep_by_space',
			'p_sign_posn',
			'path_separator',
			'pathinfo_basename',
			'pathinfo_dirname',
			'pathinfo_extension',
			'pear_extension_dir',
			'pear_install_dir',
			'php_bindir',
			'php_config_file_path',
			'php_config_file_scan_dir',
			'php_datadir',
			'php_debug',
			'php_eol',
			'php_extension_dir',
			'php_extra_version',
			'php_int_max',
			'php_int_size',
			'php_libdir',
			'php_localstatedir',
			'php_major_version',
			'php_maxpathlen',
			'php_minor_version',
			'php_os',
			'php_output_handler_cont',
			'php_output_handler_end',
			'php_output_handler_start',
			'php_prefix',
			'php_release_version',
			'php_sapi',
			'php_shlib_suffix',
			'php_sysconfdir',
			'php_version',
			'php_version_id',
			'php_windows_nt_domain_controller',
			'php_windows_nt_server',
			'php_windows_nt_workstation',
			'php_windows_version_build',
			'php_windows_version_major',
			'php_windows_version_minor',
			'php_windows_version_platform',
			'php_windows_version_producttype',
			'php_windows_version_sp_major',
			'php_windows_version_sp_minor',
			'php_windows_version_suitemask',
			'php_zts',
			'pm_str',
			'positive_sign',
			'print',
			'private',
			'protected',
			'public',
			'radixchar',
			'require_once',
			'seek_cur',
			'seek_end',
			'seek_set',
			'sort_asc',
			'sort_desc',
			'sort_numeric',
			'sort_regular',
			'sort_string',
			'static',
			'str_pad_both',
			'str_pad_left',
			'str_pad_right',
			'switch',
			't_fmt',
			't_fmt_ampm',
			'thousands_sep',
			'thousep',
			'throw',
			'try',
			'unset',
			'var',
			'yesexpr',
			'yesstr' )
	
			;
	
}

?>