<"mysqli_connect")){
        return true;
      } else {
        return false;
      }
    }
    //Function to connect to the database.
    private function connect (){
      try {
        //Mysqli functionality.
        if ($this->mysqliinstalled()){
          if (!$this->db = new mysqli ($this->host,$this->user,$this->pass)){
            $exceptionstring = "Error connection to database: <br />";
            $exceptionstring .= mysqli_connect_errno() . ": " . mysqli_connect_error();
            throw new exception ($exceptionstring);
          }
        //Mysql functionality.
        } else {
          if (!$this->db = mysql_connect ($this->host,$this->user,$this->pass)){
            $exceptionstring = "Error connection to database: <br />";
            $exceptionstring .= mysql_errno() . ": " . mysql_error();
            throw new exception ($exceptionstring);
          }
        }
      } catch (exception $e) {
        echo $e->getmessage();
      }
    }
    //Function to select a database.
    public function selectdb ($thedb){
      try {
        //Mysqli functionality.
        if ($this->mysqliinstalled()){
          if (!$this->db->select_db ($thedb)){
            $exceptionstring = "Error opening database: $thedb: <br />";
            $exceptionstring .= $this->db->errno . ": " . $this->db->error;
            throw new exception ($exceptionstring);
          }
        //Mysql functionality.
        } else {
          if (!mysql_select_db ($thedb, $this->db)){
            $exceptionstring = "Error opening database: $thedb: <br />";
            $exceptionstring .= mysql_errno() . ": " . mysql_error();
            throw new exception ($exceptionstring);
          }
        }
      } catch (exception $e) {
        echo $e->getmessage();
      }
    }
    //Function to perform a query.
    public function execute ($thequery){
      try {
        //Mysqli functionality.
        if ($this->mysqliinstalled()){
          if (!$this->db->query ($thequery)){
            $exceptionstring = "Error performing query: $thequery: <br />";
            $exceptionstring .= $this->db->errno . ": " . $this->db->error;
            throw new exception ($exceptionstring);
          } else {
            echo "Query performed correctly: " . $this->db->affected_rows . " row(s) affected.<br />";
          }
        //Mysql functionality.
        } else {
          if (!mysql_query ($thequery, $this->db)){
            $exceptionstring = "Error performing query: $thequery: <br />";
            $exceptionstring .= mysql_errno() . ": " . mysql_error();
            throw new exception ($exceptionstring);
          } else {
            echo "Query performed correctly: " . mysql_affected_rows () . " row(s) affected.<br />";
          }
        }
      } catch (exception $e) {
        echo $e->getmessage();
      }
    }
    //Function to return a row set.
    public function getrows ($thequery){
      try {
        //Mysqli functionality.
        if ($this->mysqliinstalled()){
          if ($result = $this->db->query ($thequery)){
            $returnarr = array ();
            while ($adata = $result->fetch_array ()){
              $returnarr = array_merge ($returnarr,$adata);
            }
            return $returnarr;
          } else {
            $exceptionstring = "Error performing query: $thequery: <br />";
            $exceptionstring .= $this->db->errno . ": " . $this->db->error;
            throw new exception ($exceptionstring);
          }
        //Mysql functionality.
        } else {
          if (!$aquery = mysql_query ($thequery)){
            $exceptionstring = "Error performing query: $thequery: <br />";
            $exceptionstring .= mysql_errno() . ": " . mysql_error();
            throw new exception ($exceptionstring);
          } else {
            $returnarr = array ();
            while ($adata = mysql_fetch_array ($aquery)){
              $returnarr = array_merge ($returnarr,$adata);
            }
            return $returnarr;
          }
        }
      } catch (exception $e) {
        echo $e->getmessage();
      }
    }
    //Function to close the database link.
    public function __destruct() {
      try {
        //Mysqli functionality.
        if ($this->mysqliinstalled()){
          if (!$this->db->close()){
            $exceptionstring = "Error closing connection: <br />";
            $exceptionstring .= $this->db->errno . ": " . $this->db->error;
            throw new exception ($exceptionstring);
          }
        //Mysql functionality.
        } else {
          if (!mysql_close ($this->db)){
            $exceptionstring = "Error closing connection: <br />";
            $exceptionstring .= mysql_errno() . ": " . mysql_error();
            throw new exception ($exceptionstring);
          }
        }
      } catch (exception $e) {
        echo $e->getmessage();
      }
    }
  }
  //Now, let us create an instance of mydb.
  $mydb = new mydb ("localhost","root","");
  //Select a database to use.
  $mydb->selectdb ("wps");
  //Now, let's perform an action.
  //$adata = $mydb->execute ("UPDATE cd SET title='Hybrid Theory' WHERE cdid='2'");
  //Then, let's try to return a row set.
  $adata = $mydb->getrows ("SELECT * FROM wp_terms");
  for ($i = 0; $i < count ($adata); $i++){
    echo $adata[$i] . "<br />";
  }
  $mydb->selectdb("test");
  $result = $mydb->execute("UPDATE user SET age = 23 WHERE id = 2");
  echo "<br />";
  echo $result;
"_blank" href="https://www.jb51.net/Special/84.htm">php+mysql数据库操作入门教程》、《PHP基于pdo操作数据库技巧总结》、《PHP+MongoDB数据库操作技巧大全》、《php+Oracle数据库程序设计技巧总结》、《php+mssql数据库程序设计技巧总结》、《php+redis数据库程序设计技巧总结》、《php+mysqli数据库程序设计技巧总结》及《php常见数据库操作技巧汇总》

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