Database abstraction class definition

This class is simply a front for MySQL. It is published here in support of AAWS class definition.

Code

<?php
if ( !defined( 'MYSTORE' ) ) {
	die( 'This file is not a valid entry point' );
}

class DBClass {
	/* credentials to connect to MySQL server */
	const dbHost = 'localhost';
	const dbLogin = 'mystore_login'; 
	const dbPass = 'mystore_password'; 
	
	/* a default db to connect */
	var $dbName ='mystore_database';

	/* one link to connect them all */
	private static $mysql_link = false;

	/* the DBClass object created by DBClass::get_object()   */
	private static $theObj = false;
	
	var $link;
	var $errMsg;
	var $wait;
	var $ready;
	var $result;
	

	/* 
		class function returns an instance of a DBClass
			$db_obj = DBClass::get_object();
	*/
	public static function get_object() {
		if(self::$theObj) return self::$theObj;
		
		self::$theObj = new self();
		return self::$theObj;
	}
	
	function __construct() {
		$this->errMsg = '';
		$this->wait = 200000; // 0.2 seconds
		$this->ready = False;
		if(	! self::$mysql_link ) {
			$this->connect();
		}
		if(	self::$mysql_link )
			$this->selectDB();

	} //end function queryClass


	function connect() {
		//simply connects to the host with login and password.
		if (! (	self::dbHost
				&& self::dbLogin
				&& self::dbPass) ) {
			$this->errMsg = 'Connection parameters not defined.';
			return False;
		}
		$wait = $this->wait;
		for($y=0 ; $y < 5; $y++) {
			self::$mysql_link = mysql_connect(self::dbHost, self::dbLogin, self::dbPass) ;
			if (self::$mysql_link) break;
			usleep($wait); $wait += $wait ; //increase wait each failure
		}
		if (! self::$mysql_link) {
			$this->errMsg = 'Cannot establish link to DB host: '.self::dbHost;
			return False;
		}
		return True;
	} //end function linkToDB
	
	
	function selectDB($dbName = '') {
		//selects the database. Most applications will have all tables
		//in a single database, but sometimes there are multiple. 
		if($dbName) $this->dbName = $dbName; 
		if (! $this->dbName) {
			$this->errMsg = 'DB Name not defined.';
			return False;
		}
		$wait = $this->wait;
		$this->errMsg = '';
		for($y=0 ; $y < 5; $y++) {
			$db = mysql_select_db($this->dbName, self::$mysql_link);
			if ( $db ) break;
			usleep($wait); $wait += $wait ; //increase wait each failure
		}
		if (! $db ) {
			$this->errMsg = "Cannot select DB `{$this->dbName}`.";
			return False;
		}
		$this->ready = True;
		return True;
	} //end function linkToDB


	function close_link() {
		mysql_free_result(self::$mysql_link);
		mysql_close(self::$mysql_link);
		$this->ready = False;
	}


	//this is the main funnel for all queries
	function &query($query) {
		//Returns result, and also caches it in $this->result.
		if (! $this->ready ) return false;
		unset($this->result);
		$this->errMsg = '';
		//PHP reuses connections, which means you can never know which 
		//database this script is currently connected to. 
		//For that reason, this function always calls selectDB() first
		if (! $this->selectDB()) return false;
		// ---Performing SQL query 
		$this->result = mysql_query($query, self::$mysql_link) ;
		//---calling code responsible for freeing result
		return $this->result;
	}


	
	//These simply return info about last query
	function error_number() {
		return mysql_errno( self::$mysql_link );
	}

	function error_message() {
		return mysql_error( self::$mysql_link );
	}
	
	function result_rows($result = false) {
		if($result) {
			if(is_resource($result))
				return mysql_num_rows($result );
			else return 0;
		}
		else {
			if(is_resource ($this->result))
				return mysql_num_rows( $this->result );
			else return 0;
		}
	}
	
	function affectedOnLastQuery() {
		if (! $this->ready ) return false;
		$affected = mysql_affected_rows(self::$mysql_link) ;
		return $affected;
	}
	
	function insertIdOnLastQuery() {
		if (! $this->ready ) return false;
		$id = mysql_insert_id(self::$mysql_link) ;
		return $id;
	}

	function get_row($result=false) {
		if($result) return mysql_fetch_object($result);
		if($this->result) return mysql_fetch_object($this->result);
		return false;
	}

	function free_result($result = false) {
		if($result) {
			if(is_resource($result))
				mysql_free_result($result);
		}
		else {
			if(is_resource ($this->result))
				mysql_free_result($this->result);
		}
	}
	
	function escape_string($string='') {
		return mysql_real_escape_string($string, self::$mysql_link);
	}
	/* return string for use in a SET `fld`="value" */

	function escape_set($fld, $str) {
		return '`'.$fld.'`="' . $this->escape_string($str) . '"';
	}
	function escape_null_set($fld, $str) {
		if($str===null)
			return '`'.$fld.'`='.'NULL';
		return '`'.$fld.'`="'.$this->escape_string($str) . '"';
	}
	
	/* convert a row array to a series of SET parameters */
	function get_set($array) {
		$setarr = array();
		foreach($array as $fld=>$val) {
			$setarr[] = $this->escape_set(fld, $val);
		}
		return implode(',', $setarr);
	}
}