$something = 0;
echo ('password123' == $something) ? 'true' : 'false';

'1e3' == '1000' // true

/**
 * Singleton class
 *
 */
final class UserFactory {
    /**
     * Call this method to get singleton
     *
     * @return UserFactory
     */
    public static
    function Instance() {
        static $inst = null;
        if ($inst === null) {
            $inst = new UserFactory();
        }
        return $inst;
    }

    /**
     * Private ctor so nobody else can instantiate it
     *
     */
    private
    function __construct() {

    }
}

$fact = UserFactory::Instance();
$fact2 = UserFactory::Instance();

$fact = new UserFactory()

$name = $firstName ?? $username ?? $placeholder ?? "Guest"; 

function adder(&$str2) {  
    $str2 .= 'Call By Reference';  
}
$str = 'This is ';  
adder($str);  
echo $str;  

This is Call By Reference

$a = "Original";
$my_array = array("a" => "Cat","b" => "Dog", "c" => "Horse");
extract($my_array);
echo "\$a = $a; \$b = $b; \$c = $c";

$a = Cat; $b = Dog; $c = Horse

public function getTotal($tax)
{
    $total = 0.00;

    $callback =
        function ($quantity, $product) use ($tax, &$total)
        {
            $pricePerItem = constant(__CLASS__ . "::PRICE_" .
                strtoupper($product));
            $total += ($pricePerItem * $quantity) * ($tax + 1.0);
        };

    array_walk($this->products, $callback);
    return round($total, 2);
}

class Car {
    public static
    function run() {
        return static::getName();
    }
    private static
    function getName() {
        return 'Car';
    }
}

class Toyota extends Car {
    public static
    function getName() {
        return 'Toyota';
    }
}

echo Car::run(); // Output: Car
echo Toyota::run(); // Output: Toyota

$start = microtime(true);
while (...) {

}
$time_elapsed_secs = microtime(true) - $start;

//We have this:
$objectA->a;
$objectA->b;
$objectB->c;
$objectB->d;

//We want the easiest way to get:
$objectC->a;
$objectC->b;
$objectC->c;
$objectC->d;

$obj_merged = (object) array_merge((array) $obj1, (array) $obj2);

foreach($objectA as $k => $v) $objectB->$k = $v;

 //Comparing Integers
echo 1 <= > 1; //outputs 0
echo 3 <= > 4; //outputs -1
echo 4 <= > 3; //outputs 1

//String Comparison

echo "x" <= > "x"; // 0
echo "x" <= > "y"; //-1
echo "y" <= > "x"; //1

class Student 
{
   protected $id;
   protected $name;
   // etc.

   public function __construct($id){
       $this->id = $id;
      // other members are still uninitialised
   }

   public function __construct($row_from_database){
       $this->id = $row_from_database->id;
       $this->name = $row_from_database->name;
       // etc.
   }
}

 class Student
{
    public function __construct() {
        // allocate your stuff
    }

    public static function withID( $id ) {
        $instance = new self();
        $instance->loadByID( $id );
        return $instance;
    }

    public static function withRow( array $row ) {
        $instance = new self();
        $instance->fill( $row );
        return $instance;
    }

    protected function loadByID( $id ) {
        // do query
        $row = my_awesome_db_access_stuff( $id );
        $this->fill( $row );
    }

    protected function fill( array $row ) {
        // fill all properties from array
    }
}

$student = Student::withID( $id );

class Student
{
    protected $firstName;
    protected $lastName;
    // etc.

    /**
     * Constructor
     */
    public function __construct() {
        // allocate your stuff
    }

    /**
     * Static constructor / factory
     */
    public static function create() {
        $instance = new self();
        return $instance;
    }

    /**
     * FirstName setter - fluent style
     */
    public function setFirstName( $firstName) {
        $this->firstName = $firstName;
        return $this;
    }

    /**
     * LastName setter - fluent style
     */
    public function setLastName( $lastName) {
        $this->lastName = $lastName;
        return $this;
    }
}

// create instance
$student= Student::create()->setFirstName("John")->setLastName("Doe");

function myFunc() {
    for ($i = 0; $i < func_num_args(); $i++) {
        printf("Argument %d: %s\n", $i, func_get_arg($i));
    }
}

/*
Argument 0: a
Argument 1: 2
Argument 2: 3.5
*/
myFunc('a', 2, 3.5);