本文实例讲述了PHP基于单例模式实现的数据库操作基类。分享给大家供大家参考，具体如下：

配置文件：

$db = array(

'host'=>'localhost',

'user'=>'root',

'password'=>'',

'database'=>'test',

)

?>

php 数据库基类：

class db {

public $conn;

public static $sql;

public static $instance=null;

private function __construct(){

require_once('db.config.php');

$this->conn = mysql_connect($db['host'],$db['user'],$db['password']);

if(!mysql_select_db($db['database'],$this->conn)){

echo "失败";

};

mysql_query('set names utf8',$this->conn);

}

public static function getInstance(){

if(is_null(self::$instance)){

self::$instance = new db;

}

return self::$instance;

}

/**

* 查询数据库

*/

public function select($table,$condition=array(),$field = array()){

$where='';

if(!empty($condition)){

foreach($condition as $k=>$v){

$where.=$k."='".$v."' and ";

}

$where='where '.$where .'1=1';

}

$fieldstr = '';

if(!empty($field)){

foreach($field as $k=>$v){

$fieldstr.= $v.',';

}

$fieldstr = rtrim($fieldstr,',');

}else{

$fieldstr = '*';

}

self::$sql = "select {$fieldstr} from {$table} {$where}";

$result=mysql_query(self::$sql,$this->conn);

$resuleRow = array();

$i = 0;

while($row=mysql_fetch_assoc($result)){

foreach($row as $k=>$v){

$resuleRow[$i][$k] = $v;

}

$i++;

}

return $resuleRow;

}

/**

* 添加一条记录

*/

public function insert($table,$data){

$values = '';

$datas = '';

foreach($data as $k=>$v){

$values.=$k.',';

$datas.="'$v'".',';

}

$values = rtrim($values,',');

$datas = rtrim($datas,',');

self::$sql = "INSERT INTO {$table} ({$values}) VALUES ({$datas})";

if(mysql_query(self::$sql)){

return mysql_insert_id();

}else{

return false;

};

}

/**

* 修改一条记录

*/

public function update($table,$data,$condition=array()){

$where='';

if(!empty($condition)){

foreach($condition as $k=>$v){

$where.=$k."='".$v."' and ";

}

$where='where '.$where .'1=1';

}

$updatastr = '';

if(!empty($data)){

foreach($data as $k=>$v){

$updatastr.= $k."='".$v."',";

}

$updatastr = 'set '.rtrim($updatastr,',');

}

self::$sql = "update {$table} {$updatastr} {$where}";

return mysql_query(self::$sql);

}

/**

* 删除记录

*/

public function delete($table,$condition){

$where='';

if(!empty($condition)){

foreach($condition as $k=>$v){

$where.=$k."='".$v."' and ";

}

$where='where '.$where .'1=1';

}

self::$sql = "delete from {$table} {$where}";

return mysql_query(self::$sql);

}

public static function getLastSql(){

echo self::$sql;

}

}

$db = db::getInstance();

//$list = $db->select('demo',array('name'=>'tom','password'=>'ds'),array('name','password'));

//echo $db->insert('demo',array('name'=>'脚本之家','password'=>'123'));

//echo $db->update('demo',array("name"=>'xxx',"password"=>'123'),array('id'=>1));

echo $db->delete('demo',array('id'=>'2'));

db::getLastSql();

echo "

";

?>

希望本文所述对大家PHP程序设计有所帮助。