class?

jwilson122

Hey, I was wondering if anyone could give me an example script or show me how to make a class like such:

$do->Query("SELECT * FROM users")->Where("id = 1")->extra("LIMIT 1");

See, I know how to make a class and functions inside of the class to make:

$do->Query("SELECT * FROM users");
$do->Where(""id = 1");
$do->extra("LIMIT 1");

But I would rather have the single line link..

$do->Query("SELECT * FROM users")->Where("id = 1")->extra("LIMIT 1");

Is this considered OOP (object oriented programming) ? I've searched and searched for this, tried many things.. nothings working :/ any help? Thanks!

NogDog

Chaining can be done if you have each method that you want to be able to chain return an object that contains the method you want to chain onto the end. Typically this will be by returning $this, assuming you want to chain multiple methods from the same class. So in your case, you might need a class variable that stores the query string (or perhaps several variables for each section of the query), then each method would return $this while saving its portion of the query string to the applicable class variable. (Unless someone knows of s simpler way?)

jwilson122

NogDog;10967271 wrote:
Chaining can be done if you have each method that you want to be able to chain return an object that contains the method you want to chain onto the end. Typically this will be by returning $this, assuming you want to chain multiple methods from the same class. So in your case, you might need a class variable that stores the query string (or perhaps several variables for each section of the query), then each method would return $this while saving its portion of the query string to the applicable class variable. (Unless someone knows of s simpler way?)

Sorry, didn't exactly follow what you meant.. could you show me a quick example?

NogDog

Not claiming this is necessarily how I'd do it, but it should give you the idea:

<?php
class MyDB extends mysqli
{
   private $table;
   private $columns = array();
   private $where = array();

   public function __construct($host, $user, $pwd, $database)
   {
      parent::__construct($host, $user, $pwd, $database);
   }

   public function select($column)
   {
      $columns = preg_split('/\s*,\s*/', trim($column));
      foreach($columns as $col) {
         $this->columns[] = "`$col`";
      }
      return $this; // <----------------
   }

   public function from($table)
   {
      $this->table = $table;
      return $this; // <---------------
   }

   public function where($col, $val)
   {
      $str = "`$col` = ";
      if(is_numeric($val)) {
         $str .= $val;
      } else {
         $str .= "'" . $this->real_escape_string($val) . "'";
      }
      $this->where[] = $str;
      return $this; // <---------------
   }

   public function exec()
   {
      $sql = "SELECT " . implode(',', $this->columns) . " FROM `" .
             $this->table . "`";
      if(!empty($this->where)) {
         $sql .= " WHERE " . implode (" AND ", $this->where);
      }
      // DEMO ONLY:
      echo $sql;
      // actual code would execute query and return MySQLi_Result object
   }
}

// DEMO:
$test = new MyDB('localhost', '*****', '*****', 'db_name');
$test->select('foo,bar')
     ->from('fubar')
     ->where('id', 1)
     ->where('name', 'John')
     ->exec();

Output:

SELECT `foo`,`bar` FROM fubar WHERE `id` = 1 AND `name` = 'John'

jwilson122

Would you guys recommend just doing like..

$_db->query("SELECT * FROM bla bla");

?? Or making a class chain?

NogDog

jwilson122;10967281 wrote:
Would you guys recommend just doing like..
$_db->query("SELECT * FROM bla bla");
?? Or making a class chain?

There is nothing magical about using a method chain, it's just another tool in your tool box to be used when you find it useful. Choose the tool that helps you do what you want to do in the best combination of efficiency and maintainability.

From an efficiency standpoint, if you already know what DB query you need to use and can execute it by calling one function, that is almost certainly going to be more efficient than calling a chain of several object methods. But if you find that method chain helps you create more flexible and easy-to-maintain code, then it might well be worth it to you to do so. But neither way is necessarily the "best" way, just "a" way to do it.

jwilson122

NogDog;10967285 wrote:
There is nothing magical about using a method chain, it's just another tool in your tool box to be used when you find it useful. Choose the tool that helps you do what you want to do in the best combination of efficiency and maintainability.

From an efficiency standpoint, if you already know what DB query you need to use and can execute it by calling one function, that is almost certainly going to be more efficient than calling a chain of several object methods. But if you find that method chain helps you create more flexible and easy-to-maintain code, then it might well be worth it to you to do so. But neither way is necessarily the "best" way, just "a" way to do it.

yeah, can you or anyone tell me the best way I should go about for setting up a custom framework script?

NogDog

jwilson122;10967289 wrote:
yeah, can you or anyone tell me the best way I should go about for setting up a custom framework script?

That still depends on what exactly you want to do. I personally am pretty proficient with writing SQL, and really don't need a bunch of functions to build a query in most cases. Other users might want such a thing, or perhaps it could be used to help make the application easier to port to other DBMS's.

For instance, I've used the CodeIgniter framework on a number of projects. It provides an "active record" class which does something similar to what you describe, but I never really use it, as it takes me longer to figure out which functions to call with which arguments than to just write the query. But your mileage may vary.