errors with mysqli and its inheritance...

[Hall of Famer]

Well I tried to extend the class mysqli with its inheritance called Database, which can retrieve database info easily(in one line if done correctly). It does not work out so far, as I am getting the following errors:

 

Here is the Database Class as defined:

class Database extends mysqli{
  private $select, $create, $insert, $alter, $update, $delete, $drop;
  protected $mysql, $result, $table, $column, $where, $value, $limit, $order, $type;

  public function __construct($host, $user, $pass, $db){
    $this->mysql = new mysqli($host, $user, $pass, $db) 
	   or die("Error connecting to the database {$db}");

  }

  public function __destruct(){
$this->mysql->close();
  }

  protected function prepareQuery(){
if ($prepare = $this->mysqli->prepare($this->query)) {
  trigger_error("Problem preparing query ($this->query) ".$this->mysqli->error, E_USER_ERROR);
}
return $prepare;
  }
  
  protected function reset(){
unset($this->table);
unset($this->column);
unset($this->where);
unset($this->value);
unset($this->limit);
unset($this->order);
  }

  public function select($column){    
    $this->select = implode(",", $column);
return $this;
  }
  
  public function table($table){
    $this->table = $table;
return $this;
  }
  
  public function where($where, $comparison = "=", $logic){
    $i = 0;
    foreach ($where as $col => $val){
  $wherestring .= (is_array($comparison)) ? " {$col} {$comparison[$i]} '{$val}'" : " WHERE {$col} {$comparison} '{$val}'";
  $wherestring .= ($i < (count($where)-1))?" {$logic[$i]}" :" ";
  $i++;
}
$this->where = $wherestring;
return $this;
  }
  
  public function limit($limit){
    $this->limit = $limit;
return $this;
  }
  
  public function order($order){
    $this->order = $order;
return $this;
  }
  
  public function runquery($method){
    $query = "{$method} {$this->select} FROM {$this->table}";
if(!empty($this->where)) $query .= " WHERE {$this->where}";
if(!empty($this->limit)) $query .= " LIMIT {$this->limit}";
if(!empty($this->order)) $query .= " ORDER BY {$this->order}";
echo "The generated Query is: \n".$query;
    $this->result = parent::query($query);
    $result = parent::fetch_array($this->result);
return $result;
  } 

}

 

And this is the way I run it from a script file:

include("inc/config.php");
include("classes/class_data.php");

$db = new Database($dbhost, $dbuser, $dbpass, $dbname);
$row = $db->select(array("password","email"))->table($prefix."users")->where(array("uid"=>1, "username"=>Admin"),array("=","="),array("AND"))->limit(2)->order("uid")->runquery("SELECT");

 

It did not work, and I got the following warning and error messages:

Warning: mysqli::query() [mysqli.query]: Couldn't fetch Database in classes/class_data.php on line 70
Fatal error: Call to undefined method mysqli::fetch_array() inclass_data.php on line 71

 

I am a bit confused now since I cant seem to figure out a way to resolve this problem. Can anyone of you please help? Id appreciate it very much.

[mikosiko]

A few things caught my attention...

here

  public function __construct($host, $user, $pass, $db){
    $this->mysql = new mysqli($host, $user, $pass, $db)   // it not should be $this->mysqli to be consistent with the usage after this?
	   or die("Error connecting to the database {$db}");

 

and this

    $this->result = parent::query($query);
    $result = parent::fetch_array($this->result);

should be

    $this->result = $this->mysqli->query($query);
     $result = $this->result->fetch_array();

 

 

and finally...

- you are missing a " before Admin" and

- LIMIT should be the last part of your select... hence your select could be invalid

 

with those modifications your code works for me

 

[Hall of Famer]

It does work out nicely, thank you so much. Do you know whether its possible to still use mysqli's methods such as query() and fetch_array() if the class Database does NOT extend from class mysqli? It was originally designed this way, but wouldnt work.

[Hall of Famer]

Well to make things clear, I have the select() method that looks like this right now:

 

  public function select($action = ""){
    if(empty($this->column)) $this->column = "*";
    $query = "SELECT {$this->column} FROM {$this->table}";
$query .= (!empty($this->where))?" WHERE {$this->where}":"";
$query .= (!empty($this->order))?" ORDER BY {$this->order}":"";
$query .= (!empty($this->limit))?" LIMIT {$this->limit}":"";
    echo $query."<br>";
    $this->result = $this->mysqli->query($query);
    if($action == "row") $result = $this->result->fetch_row(); 
    if($action == "assoc") $result = $this->result->fetch_assoc();
    if($action == "array") $result = $this->result->fetch_array();
    if($action == "object")  $result = $this->result->fetch_object();
    if($action == "num") $result = $this->result->num_rows();
    $this->reset();
    return $result;
  }

 

Theoretically it should check the variable $action, which can be of any values that retrieves mysql data such as row, array, assoc, object. I just looked at mysqli's manual and found that there are still many more possible ways to fetch data. I want to use a protected method called fetch(), which also accepts the variable $action and returns results from such as mysqli->fetch_array() and mysqli->fetch_object(). If works, the script should look like this one below:

 

  public function select($action = ""){
    if(empty($this->column)) $this->column = "*";
    $query = "SELECT {$this->column} FROM {$this->table}";
$query .= (!empty($this->where))?" WHERE {$this->where}":"";
$query .= (!empty($this->order))?" ORDER BY {$this->order}":"";
$query .= (!empty($this->limit))?" LIMIT {$this->limit}":"";
    echo $query."<br>";
    $this->result = $this->mysqli->query($query);
    $result = $this->result->fetch($action)
    $this->reset();
    return $result;
  }

protected function fetch($action){
   switch($action){
     case "row":
     // fetch data using mysqli->fetch_row()
     case "assoc":
     // fetch data using mysqli->fetch_assoc()
     case "array":
     // fetch data using mysqli->fetch_array()
     case "object":
     // fetch data using mysqli->fetch_object()
     case "num":
     // returns the number of rows...
     ...
     default:
     // returns nothing
   }
  
}

 

How can I design such a protected method so that it can be accessed within the select() method and other possible future methods I write(such as mselect(), which is used to select data from more than one table)? Please help.

[Hall of Famer]

So nobody knows how to do this? o_o

[mikosiko]

well... there is a working example in the "Users Contributed notes" on the manual... basically you have to extends the MYSQLI_RESULT class

http://www.php.net/manual/en/class.mysqli-result.php