use $this->member
for non-static members, use self::$member
for static members.
Full Answer
Here is an example of correct usage of $this
and self
for non-static and static member variables:
<?php
class X {
private $non_static_member = 1;
private static $static_member = 2;
function __construct() {
echo $this->non_static_member . ' '
. self::$static_member;
}
}
new X();
?>
Here is an example of incorrect usage of $this
and self
for non-static and static member variables:
<?php
class X {
private $non_static_member = 1;
private static $static_member = 2;
function __construct() {
echo self::$non_static_member . ' '
. $this->static_member;
}
}
new X();
?>
sample PDO and how work for db connection
<pre>
<?php
class DB {
private $host;
private $user;
private $pass;
private $dbase;
private $connection;
public function __construct($host,$user,$pass,$dbase)
{
$this->host = $host;
$this->user = $user;
$this->pass = $pass;
$this->dbase = $dbase;
$this->connection = new PDO("mysql:host=$this->host;dbname=$this->dbase", $this->user, $this->pass);
}
public function connect()
{
return $this->connection;
}
public function close()
{
unset($this->connection);
return true;
}
}
$dbh = new DB('localhost','root','','inventory');
$result = $dbh->connect()->query("SELECT * FROM products")->fetchAll(PDO::FETCH_ASSOC);
print_r($result);
?>
</pre>
How __construct work on Class
<?php
/*
Magic Methods in OOP
To make the use of objects easier, PHP also provides a number of magic methods, or special methods that are called when certain common actions occur within objects. This allows developers to perform a number of useful tasks with relative ease.
Using Constructors and Destructors
When an object is instantiated, it's often desirable to set a few things right off the bat. To handle this, PHP provides the magic method __construct(), which is called automatically whenever a new object is
created.
For the purpose of illustrating the concept of constructors, add a constructor to MyClass that will output a message whenever a new instance of the class is created:
*/
class MyClass
{
public $prop1 = "I'm a class property!";
public function __construct()
{
echo 'The class "', __CLASS__, '" was initiated!<br />';
}
public function setProperty($newval)
{
$this->prop1 = $newval;
}
public function getProperty()
{
return $this->prop1 . "<br />";
}
}
// Create a new object
$obj = new MyClass;
// Get the value of $prop1
echo $obj->getProperty();
// Output a message at the end of the file
echo "End of file.<br />";
/*
Note — __CLASS__ returns the name of the class in which it is called; this is what is known as a magic constant. There are several available magic constants, which you can read more about in the PHP manual.
Reloading the file in your browser will produce the following result:
1
2
3
The class "MyClass" was initiated!
I'm a class property!
End of file.