ternary operator ?:

ternary operation is not hard but not easy to use.
it can be short form of if...else and switch...case it is used in an expression as follows :
condition ? valueIfTrue : valueIfFalse
therefore we wrote

if($i>5){
 echo 'more than 5';
}else{
 echo 'not more than 5';
}

by ternary operator we can use just only

echo ($i>5)?'more than 5':'not more than 5';

or something like

$action = (empty($_POST['action'])) ? 'default' : $_POST['action'];

instead of

if (empty($_POST['action'])) {
    $action = 'default';
} else {
    $action = $_POST['action'];
}

you can also use ?: instead of switch case too.
switch ($i) { case 0: echo "i equals 0"; break; case 1: echo "i equals 1"; break; case 2: echo "i equals 2"; break; default: echo "i is not equal to 0, 1 or 2"; } // also the same as switch ($i): case 0: echo "i equals 0"; break; case 1: echo "i equals 1"; break; case 2: echo "i equals 2"; break; default: echo "i is not equal to 0, 1 or 2"; endswitch; // can also with ternary operator echo ($i==0)?"i equals 0": (($i==1)?"i equals 1": (($i==2)?"i equals 2": "i is not equal to 0, 1 or 2"));