DB Handler Concept.

[eddedwards]

Ive been studying abstract classes and interfaces and was trying to come up with a good way of using it for a database handler. I want it for a cms project im doing and would like to know if this is a good way of doing it.

 

c_db_handler.php:

1. Function for getting the handler.

2. Abstract db_handler class.

3+ Supported db extension classes.

(Currently working with SQLite and MySql skeleton in place)

<?php

function get_db_handler ($db_type) {
   $args = func_get_args();
   switch ($args[0]) {
      case "SQLite" :
         if (func_num_args() == 3) return new sqlite_handler($args[1],$args[2]);
      break;
      case "MySQL" :
         return new mysql_handler();
      break;
   }
}

abstract class db_handler {

   // Possible data connection requirements.
   protected $db_name;
   protected $db_path;
   protected $db_perm;
   protected $db_server;
   protected $db_user;
   protected $db_pass;

   // DB Handler Variables.
   protected $handle;
   protected $result;
   protected $errors = array();
   protected $result_type;

   abstract protected function connect();
   abstract protected function disconnect();
   abstract protected function parse_query($sql);
   abstract protected function parse_query_exec($sql);
   abstract public function fetch_result($fetch_type);

   function set_data($name=NULL,$path=NULL,$perm=NULL,$server=NULL,$user=NULL,$pass=NULL,$res_type=SQLITE_ASSOC) {
      if ($name) $this->db_name = $name;
      if ($path) $this->db_path = $path;
      if ($perm) $this->db_perm = $perm;
      if ($server) $this->db_server = $server;
      if ($user) $this->db_user = $user;
      if ($pass) $this->db_pass = $pass;
      $this->result_type = $res_type;
   }

}

class sqlite_handler extends db_handler {

   function __construct($db_path,$db_name) {
      $this->set_data($db_name,$db_path,0666,NULL,NULL,NULL);
   }  
   
   function connect() {
      if ($this->handle = sqlite_open($this->db_path . $this->db_name,$this->db_perm,&$this->errors[])) {
         return true;
      } else {
         return false;
      }
   }
   
   function disconnect() {
      sqlite_close($this->handle);
   }   
   
   function parse_query($sql) {
      if ($this->result = sqlite_query($this->handle,$sql,$this->result_type,&$this->errors[])) {
         return true;
      } else {
         return false;
      }
   }
   
   function parse_query_exec ($sql) {
      if ($this->result = sqlite_exec($this->handle,$sql,&$this->errors[])) {
         return true;
      } else {
         return false;
      }
   }
   
   function fetch_result($fetch_type) {
      $data = false;
      switch (strtolower($fetch_type)) {
         case "all" :
            if ($data = sqlite_fetch_all($this->result, $this->result_type)) return $data;
         break;

         case "array" :
            if ($data = sqlite_fetch_array($this->result, $this->result_type)) return $data;
         break;

         case "string" OR "single" :
            if ($data = sqlite_fetch_single($this->result)) return $data;
         break;
      }
      return $data;
   }
   
}

class mysql_handler extends db_handler {

   function connect() {
   }

   function disconnect() {
   }   
   
   function parse_query($sql) {
   }
   
   function parse_query_exec ($sql) {
   }
   
   function fetch_result($fetch_type) {
   }
   
}

?>

 

index.php:

Usage code.

<?php

include_once("./inc/c_db_handler.php");

$sql[1] = <<<SQL
BEGIN;
CREATE TABLE test ( 
   foo VARCHAR(10),
   bar VARCHAR(10)
);

INSERT INTO test (foo,bar) VALUES ("test1","test2");
COMMIT;
SQL;

$sql[2] = <<<SQL
SELECT * FROM test;
SQL;

$db = get_db_handler("SQLite",NULL,":memory:");
$db->connect();
$db->parse_query_exec($sql[1]);
$db->parse_query($sql[2]);

//$end = $db->fetch_result("all");

while ($row = $db->fetch_result("array") ) {
   $end .= "<pre>" . print_r($row,true) . "</pre>";
}

$db->disconnect();

echo "<pre>" . print_r($db,true) . "</pre>";
echo "<pre>" . print_r($end,true) . "</pre>";

?>

 

output of this test:

sqlite_handler Object
(
    [db_name:protected] => :memory:
    [db_path:protected] => 
    [db_perm:protected] => 438
    [db_server:protected] => 
    [db_user:protected] => 
    [db_pass:protected] => 
    [handle:protected] => Resource id #3
    [result:protected] => Resource id #4
    [errors:protected] => Array
        (
            [0] => 
            [1] => 
            [2] => 
        )

    [result_type:protected] => 1
)

Array
(
    [foo] => test1
    [bar] => test2
)

[corbin]

I don't like how get_db_handler is a function floating around in the global scope.

 

function fetch_result($fetch_type) {
      $data = false;
      switch (strtolower($fetch_type)) {
         case "all" :
            if ($data = sqlite_fetch_all($this->result, $this->result_type)) return $data;
         break;

         case "array" :
            if ($data = sqlite_fetch_array($this->result, $this->result_type)) return $data;
         break;

         case "string" OR "single" :
            if ($data = sqlite_fetch_single($this->result)) return $data;
         break;
      }
      return $data;
   }

 

 

 

That just seems kinda... Not elegant for lack of a better word.  Setting $res_type earlier and then passing an arg again and what not.  Also, all the switching....  I would probably put each in its own function.  fetch_array(), fetch_assoc(), fetch_row(), so on.

 

I don't remember if I saw anything else when I read through it....  Don't feel like glancing through it again, so I'm going to assume everything else was good ;p.

[eddedwards]

Cheers for the input. Id like some clarification if possible.

 

1: get_db_handler was in the global scope because I could figure out a way of doing it another way. I need to pass a database type from a config array then load the right extension. I didn't think it would work from inside the db_handler class or its extensions unless something like this is possible:

 

<?php
class db_h {

   var $db_type;

   function __construct($type) {
      $class = $type . "_h";
      $this->db_type = new $class();
   }

}

class sqlite_h {
}

$test = new db_h("sqlite");
?>

 

 

2: I can see what you mean about the set_data & the switching though I shall look into tidying that up.

 

Thanks again im going to go test my theory.

[corbin]

Yup, that's possible.