Ternary

The ternary operator ? : is a shorthand for if statements. It is an expression, so it evaluates to a value. For example:

$days_in_feb = is_leap_year($year) ? 29 : 28;

It takes three operands e1 ? e2 : e3. If the bool e1 evaluates to true, then the result is the evaluation of e2. If e1 evalutes to false, the result is the evaluation of e3.

Elvis Operator

There is also a two operand version ?:, sometimes called the "elvis operator". If the first operand is true, the whole expression evalutes to true. If the first operand is false, the whole expression evalutes to the second operand. For example:

$x = foo() ?: bar();

// Is equivalent to:
$tmp = foo();
$x = $tmp ? $tmp : bar();