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discuz db 类

class Mysql{
private $host; //主机名
private $username; //用户名
private $password; //密码
private $dbname; //数据库名
private $conn; //链接资源
private $pconnect; //是否持久连接
private $charset; //数据库编码
public $histories; //保存执行的sql语句
public $querynum = 0;  //查询的次数

//构造函数,初始化时连接数据库
public function __construct($host, $username, $password, $dbname, $charset, $pconnect = 0){
    $this->host = $host;
    $this->username = $username;
    $this->password = $password;
    $this->dbname = $dbname;
    $this->charset = $charset;
    if($pconnect){
        if(!$this->conn = mysql_pconnect($this->host,$this->username,$this->password)){
            $this->halt('Cannot connect to mysql');
        }
    }else{
        if(!$this->conn = mysql_connect($this->host,$this->username,$this->password)){
            $this->halt('Cannot connect to mysql');
        }
    }
    mysql_select_db($this->dbname);
    mysql_query("SET NAMES {$this->charset}");
}
//使用mysql_unbuffered_query不会使用缓冲区,但是它也有缺点,比如你不能使用mysql_num_rows来取得它结果的数量。
function query($sql, $type = '', $cachetime = FALSE) {
    $func = $type == 'UNBUFFERED' && @function_exists('mysql_unbuffered_query') ? 'mysql_unbuffered_query' : 'mysql_query';
    if(!($query = $func($sql, $this->conn)) && $type != 'SILENT') {
        $this->halt('MySQL Query Error', $sql);
    }
    $this->querynum++;
    $this->histories[] = $sql;
    return $query;
}
//默认返回关联数组
public function fetch_array($query, $result_type = MYSQL_ASSOC) {
    return mysql_fetch_array($query, $result_type);
}
//返回第一行第一列
function result_first($sql) {
    $query = $this->query($sql);
    return $this->result($query, 0);
}

//返回第一行数据
function fetch_first($sql) {
    $query = $this->query($sql);
    return $this->fetch_array($query);
}

function fetch_all($sql, $id = '') {
    $arr = array();
    $query = $this->query($sql);
    while($data = $this->fetch_array($query)) {
        $id ? $arr[$data[$id]] = $data : $arr[] = $data;
    }
    return $arr;
}
function affected_rows() {
    return mysql_affected_rows($this->conn);
}

function error() {
    return (($this->conn) ? mysql_error($this->conn) : mysql_error());
}

function errno() {
    return intval(($this->conn) ? mysql_errno($this->conn) : mysql_errno());
}

function result($query, $row) {
    $query = @mysql_result($query, $row);
    return $query;
}

function num_rows($query) {
    $query = mysql_num_rows($query);
    return $query;
}
   //返回字段的数目
function num_fields($query) {
    return mysql_num_fields($query);
}

function free_result($query) {
    return mysql_free_result($query);
}
//如果 AUTO_INCREMENT 的列的类型是 BIGINT,则 mysql_insert_id() 返回的值将不正确,但是可以用LAST_INSERT_ID() 来替代
function insert_id() {
    return ($id = mysql_insert_id($this->conn)) >= 0 ? $id : $this->result($this->query("SELECT last_insert_id()"), 0);
}

function fetch_row($query) {
    $query = mysql_fetch_row($query);
    return $query;
}
//取得列信息
function fetch_fields($query) {
    return mysql_fetch_field($query);
}

function version() {
    return mysql_get_server_info($this->conn);
}

function close() {
    return mysql_close($this->conn);
}
//中断提示
public function halt($message = '', $sql = ''){
    $error = mysql_error();
    $errorno = mysql_errno();
    $s = '';
    if($message) {
        $s = "<b>Error info:</b> $message<br />";
    }
    if($sql) {
        $s .= '<b>SQL:</b>'.htmlspecialchars($sql).'<br />';
    }
    $s .= '<b>Error:</b>'.$error.'<br />';
    $s .= '<b>Errno:</b>'.$errorno.'<br />';
    exit($s);
}
}

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