learning php code example

Example 1: php

<?php
class BaseClass {
   public function test() {
       echo "BaseClass::test() called\n";
   }
   
   final public function moreTesting() {
       echo "BaseClass::moreTesting() called\n";
   }
}

class ChildClass extends BaseClass {
   public function moreTesting() {
       echo "ChildClass::moreTesting() called\n";
   }
}
// Results in Fatal error: Cannot override final method BaseClass::moreTesting()
?>

Example 2: php

<?php
class Connection
{
    protected $link;
    private $dsn, $username, $password;
    
    public function __construct($dsn, $username, $password)
    {
        $this->dsn = $dsn;
        $this->username = $username;
        $this->password = $password;
        $this->connect();
    }
    
    private function connect()
    {
        $this->link = new PDO($this->dsn, $this->username, $this->password);
    }
    
    public function __sleep()
    {
        return array('dsn', 'username', 'password');
    }
    
    public function __wakeup()
    {
        $this->connect();
    }
}?>

Example 3: ?? php

?: // !empty()
?? // isset()