Lazy PDO - allows you to group all SQL in one file, and adds data accesses as services of the DB object. It is "Lazy" because accessors are prepared only when needed.

LazyPDO.php

//
//  Lazy PDO - register queries at startup, but only prepare them if they are actually used
//
  
class LPDO extends PDO
{
    private $querystrings;
 
    public function __set($property,$value)
    {
        if( is_object($value) )
        {
            $this->$property = $value;
        }
        else
        {
            $this->querystrings[$property] = $value;
        }
    }
 
    public function __get($property)
    {
        if(property_exists($this,$property))
        {
            return $this->$property;
        }
        else
        {
            //echo_r($this->querystrings[$property]);
            return $this->$property = $this->prepare($this->querystrings[$property]);
        }
   }
}

function db_connect()
{
    try{
        $db = new LPDO("mysql:host=".DB_SERVER.";dbname=".DB_NAME, DB_USER, DB_PASSWORD);
    }
    catch(PDOException $Exception) {
        die( $Exception->getMessage() );
    }

    // example query
    $db->search_inventory =
       "SELECT partnumber, photo, qty, description FROM new_inv WHERE qty >= :minq ORDER BY partnumber";
    
    // Addendum, I've started putting all the queries in their own file:
    require_once 'models/queries.php';
}

// USAGE:
$db->search_inventory->execute( array( ':minq' => WHOLESALE_MINIMUM_QTY ) );
while( $row = $search-inventory->fetch(PDO::FETCH_OBJ) ){
  //...
}