Question

I have a class Database and Class User. My problem is that I want to create an instance of Database and use it throughout my classes.

Class User is just one of them. I want to be able to get the user record from the table using the database object. I don’t want to create a database variable inside each class, because I will using sessions. Is there a solution?

class Database
{
    /*
     * Edit the following variables
     */
    private $db_host = 'localhost';     // Database Host
    private $db_user = 'root';          // Username
    private $db_pass = '';          // Password
    private $db_name = 'researchportal';          // Database
    /*
     * End edit
     */

    private $con = false;               // Checks to see if the connection is active
    private $result = array();          // Results that are returned from the query

    /*
     * Connects to the database, only one connection
     * allowed
     */
    public function connect()
    {
        if(!$this->con)
        {
            $myconn = @mysql_connect($this->db_host,$this->db_user,$this->db_pass);
            if($myconn)
            {
                $seldb = @mysql_select_db($this->db_name,$myconn);
                if($seldb)
                {
                    $this->con = true;
                    return true;
                }
                else
                {
                    return false;
                }
            }
            else
            {
                return false;
            }
        }
        else
        {
            return true;
        }
    }

    /*
    * Changes the new database, sets all current results
    * to null
    */
    public function setDatabase($name)
    {
        if($this->con)
        {
            if(@mysql_close())
            {
                $this->con = false;
                $this->results = null;
                $this->db_name = $name;
                $this->connect();
            }
        }

    }

    /*
    * Checks to see if the table exists when performing
    * queries
    */
    private function tableExists($table)
    {
        $tablesInDb = @mysql_query('SHOW TABLES FROM '.$this->db_name.' LIKE "'.$table.'"');
        if($tablesInDb)
        {
            if(mysql_num_rows($tablesInDb)==1)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }

    /*
    * Selects information from the database.
    * Required: table (the name of the table)
    * Optional: rows (the columns requested, separated by commas)
    *           where (column = value as a string)
    *           order (column DIRECTION as a string)
    */
    public function select($table, $rows = '*', $where = null, $order = null)
    {
        $q = 'SELECT '.$rows.' FROM '.$table;
        if($where != null)
            $q .= ' WHERE '.$where;
        if($order != null)
            $q .= ' ORDER BY '.$order;

        $query = @mysql_query($q);
        if($query)
        {
            $this->numResults = mysql_num_rows($query);
            for($i = 0; $i < $this->numResults; $i++)
            {
                $r = mysql_fetch_array($query);
                $key = array_keys($r);
                for($x = 0; $x < count($key); $x++)
                {
                    // Sanitizes keys so only alphavalues are allowed
                    if(!is_int($key[$x]))
                    {
                        if(mysql_num_rows($query) > 1)
                            $this->result[$i][$key[$x]] = $r[$key[$x]];
                        else if(mysql_num_rows($query) < 1)
                            $this->result = null;
                        else
                            $this->result[$key[$x]] = $r[$key[$x]];
                    }
                }
            }
            return true;
        }
        else
        {
            return false;
        }
    }

    /*
    * Insert values into the table
    * Required: table (the name of the table)
    *           values (the values to be inserted)
    * Optional: rows (if values don't match the number of rows)
    */
    public function insert($table,$values,$rows = null)
    {
        if($this->tableExists($table))
        {
            $insert = 'INSERT INTO '.$table;
            if($rows != null)
            {
                $insert .= ' ('.$rows.')';
            }

            for($i = 0; $i < count($values); $i++)
            {
                if(is_string($values[$i]))
                    $values[$i] = '"'.$values[$i].'"';
            }
            $values = implode(',',$values);
            $insert .= ' VALUES ('.$values.')';

            $ins = @mysql_query($insert);

            if($ins)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }

    /*
    * Deletes table or records where condition is true
    * Required: table (the name of the table)
    * Optional: where (condition [column =  value])
    */
    public function delete($table,$where = null)
    {
        if($this->tableExists($table))
        {
            if($where == null)
            {
                $delete = 'DELETE '.$table;
            }
            else
            {
                $delete = 'DELETE FROM '.$table.' WHERE '.$where;
            }
            $del = @mysql_query($delete);

            if($del)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        else
        {
            return false;
        }
    }

    /*
     * Updates the database with the values sent
     * Required: table (the name of the table to be updated
     *           rows (the rows/values in a key/value array
     *           where (the row/condition in an array (row,condition) )
     */
    public function update($table,$rows,$where)
    {
        if($this->tableExists($table))
        {
            // Parse the where values
            // even values (including 0) contain the where rows
            // odd values contain the clauses for the row
            for($i = 0; $i < count($where); $i++)
            {
                if($i%2 != 0)
                {
                    if(is_string($where[$i]))
                    {
                        if(($i+1) != null)
                            $where[$i] = '"'.$where[$i].'" AND ';
                        else
                            $where[$i] = '"'.$where[$i].'"';
                    }
                }
            }
            $where = implode('',$where);


            $update = 'UPDATE '.$table.' SET ';
            $keys = array_keys($rows);
            for($i = 0; $i < count($rows); $i++)
            {
                if(is_string($rows[$keys[$i]]))
                {
                    $update .= $keys[$i].'="'.$rows[$keys[$i]].'"';
                }
                else
                {
                    $update .= $keys[$i].'='.$rows[$keys[$i]];
                }

                // Parse to add commas
                if($i != count($rows)-1)
                {
                    $update .= ',';
                }
            }
            $update .= ' WHERE '.$where;
            $query = @mysql_query($update);
            if($query)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        else
        {
            return false;
        }
    }

    /*
    * Returns the result set
    */
    public function getResult()
    {
        return $this->result;
    }
}

Class User:

<?php 
require_once 'class.database.php';

    class User{
        public $usr_id;
        public $usr_name;
        public $usr_level;
        public $last_access_login;

        public function __construct($id) {
            $this->usr_id = $id;
            //$this->usr_name = $usr_name;
            //$this->usr_level = $usr_level;
            $this->last_access_login = date("F d Y H:i:s.",time());
      }

      public function getUser()
      {
    //  $db->select('login_users','*','user_id='.$this->usr_id.'');  
    //  $res = $db->getResult();  
    //  print_r($res);

        $this->usr_name = $res['username'];
        $this->usr_level = $res['user_level'];
        $this->last_access_login = date("F d Y H:i:s.",time());

      }
    }

    $a = new User(3);
    $a->getUser();

    ?>

Answer 1

You will want to either pass $database to your user constructor or use a singleton like MrJ suggested up there.

Passing your database object as a parameter is pretty simple as you already know, but you make it clearer to others:

private $myDatabase = NULL;

public function __construct(Database $myDatabase){
    $this->myDatabase = $myDatabase;
}

And then in the class anywhere you can use your database using

$this->myDatabase->select(...);

Creating the object now becomes as simple as:

$myUser = new User($database);

Obviously, adapt it as the need be 🙂

---

Singletons are also simple to use, create a static method inside your database class:

private static $staticInstance = NULL;

public static function getInstance(){
    if(Database::$staticInstance == NULL){
        Database::$staticInstance = new Database();
        Database::$staticInstance->connect();
    }
    return Database::$staticInstance;
}

This creates a function that automatically create your instance of the your unique database class as soon as you need it and return that single instance when you call the getInstance again.

To use this inside of your other classes simply call:

$mydb = Database::getInstance();

And then use your database object…

Singletons are really useful in many similar situations.