I have a quick question to you guys, i have created the CFG file which stores my database connection detail in two dimensional array. I then connect it to my PHP class file and make it launch the arrays stated in CFG file. As you can see below in my code:
cfg.php
<?php
$cfg['db']['host'] = 'localhost';
$cfg['db']['user'] = 'root'; //your user name
$cfg['db']['pass'] = ''; //your password
$cfg['db']['db'] = 'db3'; //your database
?>
and my class file :
<?php
require_once(dirname(__FILE__) . 'cfg.php');
class Database {
private $dbConn; //stores the database connection
public function __construct($dbConn)
{
global $cfg;
mysql_connect(DB_HOST,DB_USER,DB_PASSWORD) or die('Could not connect to MySQL server.');
mysql_select_db(DB_DATABASE)or die('Unable to select database: ');
}
}
What i want to ask you is: is this right way of doing this? also what do I need to add in my index to see that it is connected. and the output of the database content. Thank you in advance for taking time and reading my problem. Cheerio.
Edit :
<?php
require_once(dirname(__FILE__) . 'cfg.php');
class Database {
private $dbConn; //stores the database connection
public function __construct($dbConn)
{
global $cfg;
mysqli_connect($cfg['db']['host'], $cfg['db']['user'], $cfg['db']['pass'])
or die('Could not connect to MySQL server.');
mysqli_select_db($dbConn, $cfg['db']['db'])
or die('Unable to select database: ');
}
}
Does this looks better now? If yes. How do i connect it with the index.php file where my forms will be stored. say to output the message of (connected to database). Thank you.
EDIT: changed to mysqli and now when selecting the database it states that i am missing the database name. Not sure where to put that and how to alter it. Thank you.
EDIT: I am on my way to create functions for 'Select' 'Insert' and 'Delete' . If any of you can point me do a great source of information which will help me in my research it will be most appreciated.
You are using constants instead of the actual values from your config in your mysql_connect() function, so that wouldn't work. You would need to do it this way:
mysql_connect($cfg['db']['host'], $cfg['db']['user'], $cfg['db']['pass'])
Aside from that and OO paradigms, it would probably be better if you used PHP's mysqli (as stated here) or PDO, as PHP's mysql_ is pretty outdated.
No you are not doing it correctly. By using this line
require_once(dirname(__FILE__) . 'cfg.php');
in your class file you have introduced a somewhat tight coupling to the config file and you have made it hard to swap it out for other credentials. I.e. you will have to change the file with the Database class in it to change the credentials. So start by dropping that include there.
Another thing you do is using the global keyword which is as far from OOP as you could possibly get. Inject the information the class needs instead.
Also you are using the ancient, deprecated and soon to be removed mysql_* API. You are also calling the execution of your script of something fails (or die()) which makes it impossible to integrate your code in a project and also makes it impossible to correctly handle errors (i.e. custom error page).
When upgrading to a better database API (e.g. PDO) you even don't have the need anymore to use a database class at all.
The above would simply look something like the following:
bootstrap.php
try {
$dbConnection = new \PDO('mysql:dbname=dbtest;host=127.0.0.1;charset=utf8', 'user', 'pass');
$dbConnection->setAttribute(\PDO::ATTR_EMULATE_PREPARES, false);
$dbConnection->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
} catch (\PDOException $e) {
// nicely handle error here
}
Alternatively you could implement lazy loading for the database connection depending on your requirements.
As you can see now there is no need for an external config file (you can just change the credentials here in the bootstrap file) and there is no need for a database class.
Related
Pre-emptive apology: This post contains basic questions.However, I have searched and I have not found an answer, if there is one...sorry.
I am following some youtube tutorials for making a basic ajax web chat, and in the tutorial the person is using MySQLi to connect to the DB. I want to create the same ajax chat application except I want to use PDO instead of MySQLi.
The person uses these two files:
config.php
<?php
define('DB_HOST', 'localhost');
define('DB_USER', 'bucky_chat');
define('DB_PASSWORD', '123456');
define('DB_NAME', 'bucky_chat');
?>`
chat.class.php
<?php
require_once('config.php');
require_once('error_handler.php');
class Chat {
private $mysqli;
//constructor opens DB connection
function __construct(){
$this->mysqli = new mysqli(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
}
//destructor closes db connection
function __destruct(){
$this->mysqli->close();
}
}
?>
I'm trying to replicate the above snippets with PDO. The problem is that I'm not sure how to adapt the PDO examples I have looked at to do this.
First of all I'm confused as to why he defined these things in a separate file.. are there any benefits in doing this?
In another PDO tutorial I am looking at I see it can be done the followings way:
<?php
$config['db'] = array(
'host' => 'localhost',
'username' => '',
'password' => '',
'dbname' => ''
);
$db = new PDO('mysql:host=' . $config['db']['host'] . ';dbname=' . $config['db']['db_name'], $config['db']['username'], $config['db']['password']);
//some code
$db = null; //closes connection
?>
`
I think this is what I need to use (in a try catch block), but why does he put these things in an array? it seems to over complicate things... why not just variables? But does this code replicate the mysqli example? Howcome I don't see __construct() being used with PDO?
Some minor questions...
When creating a website with a user, is there a standard place to store DB connection?
Any book recommendations?
Sorry for all these questions, All help is strongly appreciated!
To answer your questions:
First of all I'm confused as to why he defined these things in a separate file
The authentication details are defined in a second file because if you create another query script, now both scripts can include the authentication details. If the authentication details change, you only need to update one file. If you are just writing a simple application, than just keep everything in one file.
but why does he put these things in an array
I think this is just done in-case the authentication details are needed someone else in the script (much like the defined globals from your first sample). Its often best practice to define parameters into variables (even if you use the variable once). This way, if you typo a variable, you will get an error; versus copy and pasting the same string over and over again.
Howcome I don't see __construct() being used with PDO
When ever you create a new object in PHP, you do not need to call __construct, it is called automatically with the "new" statement.
$PDOConnection = new PDO($dsn, $username, $password);
When creating a website with a user, is there a standard place to store DB connection
Definitely make sure the authentication details are stored in an inaccessible file to the public. The connection object has no harm to be accessed by the public (unless of course you need to authenticate the client (website user) before establishing a database connection). Is is best practice to always begin your (secure) PHP files with:
<?php
BUT... never end the file with "?>". If an extra character is inserted after the "?>" on accident, your web server could display your whole script to the world (of course your Apache, etc... would have to be configured wrong). Like I said... best practices.
Any book recommendations?
Googleing "php arcitechture best practices" may help.
You are confusing WAY TOO MUCH things that can be explained in one answer. you don't even know what to ask.
Please, don't take the art of programming as a some sort of cheap trick one can learn in 2 hours. To write a AJAX-based chat one need to learn for at least several months. To learn by understanding, not by copy-pasting. To learn step by step, going from variables to arrays, from arrays to functions, from functions to classes and so on - not by throwing all the code they find in one bowl and then asking on SO how to deal with all that. One cannot get to another step without having understand a previous one. And of course all these youtube tutorials are definitive pieces of useless rubbish.
some of your confusions are:
__construct() method actually has nothing to do with PDO. Nor with mysql. this is a Chat class method. And method which is all wrong. Chat class shouldn't create its own connection but use already created one.
This thing on variables vs. array vs. constants doesn't really matter. To have connection options in a separate file is a good thing but nonetheless you need to have a connection code in the separate file as well, to avoid writing connection code in the every file.
You should not use this code in a try catch block (unless you have an idea what to do in case of error, which I doubt you have).
Before starting for a chat, you have to learn smaller, simpler applications, like telephone book or the like, to learn basic database operations, from which you'll be later able to build ANY application, like any house can be built of bricks.
PDO basics you can get right here, in the tag wiki. But OOP basics is not that easy.
First the reason you define config in different file is so that you can just include that file instead of writing the database configuration anytime you want database access. It is preferred best practice.
you can do:
try
{
$PDOConnection = new PDO('mysql:host='.DB_HOST.';dbname='.DB_NAME.'', DB_USER, DB_PASS);
$PDOConnection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
//Do you stuffs
$PDOConnection = null;
}
catch(PDOException $e)
{
//Do something with error
}
Why not just do:
<?php
$hostname = 'host';
$dbname = 'dbname';
$username = 'uname';
$password = 'pw';
try {
$db = new PDO("mysql:host=$hostname;dbname=$dbname", $username, $password);
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch (PDOException $ex) {
echo "An Error occurred!";
}
?>
In a separate PHP file I call mine dbPDO.php and then have:
require_once("dbPDO.php");
In your PHP pages. And then run queries by doing:
EDIT: to condense my answer.
$username = $_POST['username'];
$stmt = $db->prepare("SELECT field1, field2, field3, etc FROM mytable WHERE username = :username");
$stmt->bindParam(':username', $username);
$stmt->execute();
while ($r = $stmt->fetch()) {
$field1 = $r['field1'];
$etc = $r['etc'];
}
Make sure you bindParam and use the ':' in the query. Don't just put WHERE username = $username or WHERE username = $_POST['username'] That would led you prone to SQL Injection. Also, I didn't show it here, but you should have some sort of exemption handling for each query. I place the whole query in a Try/Catch, but I hear there are other ways to deal with it. I personally think its personal preference.
First of all you don't need an array nor variables, you can directly input the configuration..like:
try { //try connection
//common db
$db = new PDO('mysql:host=localhost;dbname=some_db_name', 'some_usernane', 'some_pass');
$db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (Exception $e) { //connection failed
die("Oh no! It seems we took too long to respond, we are sorry for that..");
}
Secondly _constructor() means that whenever the class Chat is called everything in the _constructor() is executed .
Here is a good tutorial for PDO http://wiki.hashphp.org/PDO_Tutorial_for_MySQL_Developers
I'm kinda going crazy about this problem. I can't do it myself so I need the community to help me get this thing solved. I've been spending hours on this because I didn't know where to look. I now know a possible fix but it's just messy (read on). I just need someone who knows more about this than I do.
This is my situation:
I want to use 2 or more mysql connections.
I use OOP
I have a class called dbase, it has two functions, setConnection and getConnection and two class variables called $connection and $dbaseName.
In my main project file I include dbase and create two objects:
dbase
maindbase
then I do:
$this->dbase->setConnection($server, $uname, $pword);
$this->maindbase->setConnection($server, $uname, $pword);
the setConnection function looks like this:
function setConnection ($server, $serv_Username, $serv_Password) {
$this->connection = mysql_connect($server, $serv_Username, $serv_Password, true);
// echo $this->connection . "<BR>";
}
I echo it to see the resourcenumber and added true to mysql_connect (and I know it's deprecated since 5.5, I'm not here for that).
Now, as I understand OOP, the class variables are set per object. So $connection from dbase will never be the same as maindbase (unless, of course, I use the same credentials, but even then it will create a new link because of the $new_link option I enabled). They both have different resource ID's.
My problem:
In class dbase I also have a function which runs a query like this:
$connection = $this->getConnection();
$dbase_name = $this->getDbaseName();
mysql_select_db($dbase_name, $connection);
$q = "SELECT * FROM {$table_name} WHERE {$column} LIKE '{$value}'";
$result = mysql_query($q);
Now, when I use it like this, it will ALWAYS use the FIRST $connection that has been set in class dbase and it doesn't matter which object this is, either object dbase or maindbase.
I get this error:
Table 'testdbase1.skye_domains' doesn't exist
object dbase is connected to testdbase1
object maindbase is connected to testdbase2
the above error I get when trying to select results using the maindbase object.
When I remove the $connection string from mysql_select_db it works perfectly because it will try to open a new connection as if using mysql_connect.
Why is this? This is impossible right? How can objectmaindbase have the same $connection as object dbase? They are in NO WAY connected to eachother... Is PHP somehow using a global mysql_connect variable or buffer which I'm not aware about?
I would like to keep using connectionstrings as this is just handy now and then. Leaving the $connection string out seems messy.
Does anybody have any suggestions I can try to make PHP (or my head) sane again?
Try to put echo $this->connection EVERYWHERE you use it. Also, create an "id" member and fill it with a unique value upon constructing a dbase-object and echo it along the value of $this->connection. This way you can track where what happens to your connection.
And check if there's maybe some place outside of the class that assigns $foo->connection. If you're not using "private" on the members, you're bound to have such problems when you e.g. forget to remove a hack or an experiment from unrelated parts of your code.
I am used to mysql database access using the procedural mysql method. I am a beginner - intermediate programmer.
I am trying to learn the PDO api, however all resources which discuss using PDO show the connection string, username and password.
e.g.
<?php
try {
$db_conn = new PDO('mysql:host=localhost;dbname=databaseName','username', 'password');
}
catch (PDOException $e) {
echo 'Could not connect to database';
}
$sql = 'SELECT * FROM Products';
$stmt = $db_conn->prepare($sql);
...
...
...
?>
What I want, and think would be better programming is to put my PDO connection into a new file. then where I want to run an SQL query, I require_once('PDO.php') or similar.
The problem I have with this is as follows:
How do I close the connection? Simply $db_conn = null; ??
Should I close the connection after each query is run, then re-open the connection?
Should I close the connection or is it automatically destroyed when the user closes the browser?
I am working from a book called PHP Master: Writing Cutting Edge Code. http://www.sitepoint.com/books/phppro1/ and this has completely omitted any reference to closing the connection / destroying the object after it has been used.
Furthermore, I have looked at online tutorials, and they all connect to the database using PDO inline as opposed to having a separate database connector. This I am not happy with for many reasons:
I have to type username & password to connect every time.
If I get a developer to take a look at code / write some code, they will all have access to the database.
If I change the DB username & Password, then each file which connects to the database will need to be updated.
Could anybody recommend a better resource? Could anybody advise on what is the best practice way to do this?
Many thanks
Your question about how to store the database name, username and password have nothing to do with the capabilities of PDO. This is an implementation choice. The way you use to work with procedural functions can also be applied to PDO, the difference is that with PDO you work with objects instead.
So for simplicity, store the PDO creation of an object, either in a function or class, in which you can create the PDO instance anytime, e.g.
function createPDO($cfg) {
try {
return new PDO("mysql:host=".$cfg['host'].",port:".($cfg['port']).";dbname=".($cfg['name']).";",$cfg['username'], $cfg['password']);
} catch(PDOException $e) {
// handle exceptions accordingly
}
}
You can centralise these in whatever PHP file you like to include, just like you were used with the procedural functions.
You have two choices, either put all the relevant database information inside the createPDO, or use something like a config ($cfg) variable to store all this information.
$config = array();
$config['db'] = array(
'host' => 'localhost',
'name' => 'databse',
'username' => 'userx',
'password' => 'passy'
/* .. etc */
)
Using the createPDO function would be as followed
$db_conn = createPDO($config['db']);
For connections closing, each connection made to the database automatically disconnects after PHP exits its execution. You can however, close the connection if you wish, by setting the variable of the PDO object you assigned it to, in this example (and in yours) $db_conn to null
$db_conn = null; // connection closed.
The PDO has a manual http://php.net/manual/en/book.pdo.php here, which is a good start getting to know PDO a bit better.
You do not close the connection after a query, you simply leave it open for the next query. When PHP exists and your page is shown, the connection will be closed automatic.
It is a good idea to put the db stuff in a separate file and include that.
Even better, put all your db stuff in a class in use that.
Have a look at the pdo php page. Although not the best examples, they should get you started.
My question is I am using the variable $db in my general script code and within one of my functions. It's purpose is to be the variable that is used for MySQL connections. I have a need inside a function to write some data to the database. In my script I cannot assume that an existing db connection will be open so I open a new one and close it before the function exits. Ever since doing this I am getting an error after the script runs saying the MySQL reference is bad / doesn't exist.
The only thing I can pin it to is in my core code I use the variable $db as the variable name for database connection. I also use the same variable in the function. I did not imagine this would be a problem because I do not use global in front of $db in the function. This should mean the $db I reference in my function is in the functions private scope but it seems to be closing the public $db's connection.
Any thoughts?
Fragments of my code are:
database.php
db_connect()
{
// open mysql db connection and return it;
}
db_close( &$db )
{
// close the passed by reference db connection
}
api.php
api_verify( $keyid, $userid, $key )
{
// open a new db connection
$db = db_connect();
// check for errors. if any errors are found note them in the db
// close the db
db_close($db);
}
main.php
include api.php;
include database.php;
// open a connection to the db
$db = db_connect();
// pull a list of things to process from the db and move through them one at a time
// call api_verify() on each key before working through it's data.
db_close($db)
To manage DB connections, you can create a class rather than a pair of functions. If where you say "MySQL reference", the exact error refers to a "MySQL resource", then you are using the outdated mysql extension and should switch to a more modern extension, such as PDO.
class DBConnection {
protected static $_connections = array(),
static connect($dsn) {
if (!isset(self::$_connections[$dsn])) {
$credentials = self::getCredentials();
/* Create connection. For example: */
try {
self::$_connections[$dsn][0] = new PDO($dsn, $credentials['username'], $credentials['password']);
} catch (PDOException $exc) {
// erase the frame w/ password from call trace to prevent leak.
throw new PDOException($exc->getMessage(), $exc->getCode());
}
/* End create connection example */
self::$_connections[$dsn][0]->dsn = $dsn;
}
++self::$_connections[$dsn]['count'];
return self::$_connections[$dsn][0];
}
static close($db) {
if (isset(self::$_connections[$db->dsn])) {
if (--(self::$_connections[$db->dsn]['count']) < 1) {
unset(self::$_connections[$db->dsn]);
}
}
}
static getCredentials() {
/* credentials can be stored in configuration file or script, in this method, or some other approach of your own devising */
}
}
Note that this isn't exactly OOP (it is, but only in a technical sense). The above doesn't lend itself well to unit testing. If you want a more OO approach (which will be more amenable to unit testing), extend or wrap PDO. Using dependency injection can also help with the coupling issues of the above.
I assume you are opening a connection to the same database with the same username/password at each of the places you call db_connect. When doing so,unless your db_connect explicitly specifies, that you are creating a new link, it will return an already opened link.If that link is then closed using db_close(), it will also close the other connection, since the link is the same. If you are using mysql_connect to connect to the database, it takes an argument called new link
new_link
If a second call is made to mysql_connect() with the same arguments, no new link will be established, but instead, the link identifier of the already opened link will be returned. The new_link parameter modifies this behavior and makes mysql_connect() always open a new link, even if mysql_connect() was called before with the same parameters. In SQL safe mode, this parameter is ignored.
Refer to http://php.net/manual/en/function.mysql-connect.php
I'm not sure if this is the issue you are facing. Hope it helps.
I would assume what is happening is the connect cancels out because there already is a connection, and then the close ends the current connection.
I would recommend either A) start a connection at the beginning of the file, and just know it's always there (what I do); or B) check the to see if the $db variable is set, if not then create the connection, and always end the connection at the end of the file.
HI everyone, I was just wondering what the best way to make multiple queries against tables in a mysql databases is. Should I be making a new mysqli object for every different .php page ($mysqli = new mysqli("localhost", "root", "root", "db");)?
Or is there a way to reuse this one time over all php files in my website? Any suggestions would be pretty cool
My vote would be to take an OOP approach. I would have one script that has a DB conn class in it and a method in that class to check if a connection exists and if it does returns the connection object. You could have that db class script referenced [ include_once(); ] on the pages that need to access the database. Then it would be a matter of instantiating the db object, firing the "if-exists" method and if it returns true then just utilize the existing connection within the object.
You could also take a look at utilizing persitent connections to the DB
Persistent connections
However honestly you will be better off in the long run and scalability of your application to handle the db connection management yourself rather then leaving a connection constantly open.
Here is an example of how I would structure that class:
As a note, made by #alex, the mysql_error() should not be echoed to the page in an environment where the display_errors() is set to display all warnings. (e.g error_reporting(E_WARNING);)
class dbconn {
protected $database;
function __construct(){
$this->connect();
}
protected function connect() {
$this->database = mysql_connect('host', 'user', 'pass') or die("<p>Error connecting to the database<br /><strong>" . mysql_error() ."</strong></p>" );
mysql_select_db('databasename') or die("<p>Error selecting the database<br />" . mysql_error() . "</strong></p>");
}
function __destruct(){
mysql_close($this->database);
}
function db(){
if (!isset($this->database)) {
$this->connect();
}
return $this->database;
}
}
You need to create the connection for each page, as each PHP script's lifetime is that of the request.
However, you can place the connection code in one file and then include it from all pages.
You could create a connect.php that validates it's being included by your application, and then creates a DB connection.
You could then include that file at the beginning of your application's init, or the beginning of any independent script that needs a connection =)
Depends on structure of website. If you have:
<a herf='login.php'>login</a>
<a herf='register.php'>register</a>
<a herf='about.php'>about</a>
..., then you'll have to connect in every PHP file, i.e., in login.php, in register.php and in about.php. To make it easier, I would either create config.php file which holds user/pass, or even do like Shad said.
You might also have index.php that contains something like this:
if ( !isset($_GET['module']) ) {
$_GET['module'] = 'about';
}
switch ( $_GET['module'] ) {
default:
case 'about':
include 'about.php';
break;
case 'login':
include 'login.php';
break;
case 'register':
include 'register.php';
break;
}
And HTML code:
<a herf='?module=login'>login</a>
<a herf='?module=register'>register</a>
<a herf='?module=about'>about</a>
In this case you can connect in index.php and then pass the connection to all other involved files.
The 2nd way seems to be more common to me, i.e., it feels more intuitive, more handy and that's what I always do.
I believe that in some cases it might be worthy (performance-wise) to use persistent connections and reserve/release connection when needed (either for transaction or even for single query). For example, simple system that I'm now working with takes 70ms-100ms to generate, and it takes only 40ms-50ms to do SQL queries. If using "single connection" approach, it means that connection is wasted for about 50% of time, while "reserve/release connection when needed" with persistent connections would not have such issue.
One more thing - I would advise you to create some wrapper, i.e., some DBConnection class that connects to DB in constructor and has methods like select() (returns array of data), selectValue() (returns single value, e.g., $db->selectValue('select count(*) from user') would return (int)$numberOfUsers), some exec() for inserts and updates etc.