Database operation class based on mysqli

<?PHP/***************************** Database Access Class (Mysqli version) ******************************/classmysqlidb{//Database link itself    Private $link; //the last SQL statement executed    Private $sql; //Initialize class     Public function__construct ($hostname,$username,$password,$database){        $this->link=NewMysqli ($hostname,$username,$password,$database); if(Mysqli_connect_error()){            $errorInfo= ' error:could not make a database link ('.Mysqli_connect_errno().‘)‘.Mysqli_connect_error(); Throw NewErrorexception ($errorInfo, 1); }        $this->link->set_charset ("UTF8"); }    //gets the ID that was generated after the insert    Private functionGetlastid () {return $this->link->insert_id; }    //gets the number of rows affected    Private functioncountaffected () {return $this->link->affected_rows; }    //assemble the conditions of an array format into a string    Private functionRewhere ($where){        $str= ' '; foreach($where  as $key=$value){            if(!Empty($str)){                $str. = ' and '; }            $rekey=$this->link->escape_string ($key); $revalue=$this->link->escape_string ($value); $str.=Is_numeric($revalue)?" `$rekey`=$revalue":"`$rekey=$revalue‘"; }        return $str; }     Public functionCreate$table,$model){        $fields= ' '; $values= ' '; foreach($model  as $key=$value) {            if($fields){                $fields. = ', '; }            $fields.="`$key`"; if($values){                $values. = ', '; }            $values.=Is_numeric($value)?$value:"‘".$this->link->escape_string ($value)."‘"; }        $this->sql= "INSERT into"$table`($fields) VALUES ($values)"; Echo $this-SQL; $this->link->query ($this-SQL); return $this->link->insert_id; }     Public functionModify$table,$model,$where){        $assins= ' '; $where=$this->rewhere ($where); foreach($model  as $key=$value) {            $rkey=$this->link->escape_string ($key); $rvalue=$this->link->escape_string ($value); if(!Is_numeric($rvalue)){                $rvalue= "'".$rvalue."‘"; }            $assins.=$assins?",`$rkey`=$rvalue":"`$rkey`=$rvalue"; }        $this->sql= "UPDATE"$table' SET$assinsWHERE$where"; Echo $this-SQL; $this->link->query ($this-SQL); }     Public functionRemove$table,$where){        $where=$this->rewhere ($where); $this->sql= "DELETE from"$table' WHERE$where"; Echo $this-SQL; $this->link->query ($this-SQL); }     Public functionSearch$table,$where){        $where=$this->rewhere ($where); $this->sql= "SELECT * from"$table' WHERE$where"; $this->link->query ($this-SQL); $result=$this->link->query ($this-SQL); return $result-Fetch_assoc (); }     Public functionUnique$table,$where){        $where=$this->rewhere ($where); $this->sql= "SELECT * from"$table' WHERE$whereLIMIT 1 "; $result=$this->link->query ($this-SQL); return $result-Fetch_object (); }}

Database operation class based on mysqli