php - Meaning of question mark colon operator [duplicate]

Question

What does ?: in this line mean?

$_COOKIE['user'] ?: getusername($_COOKIE['user']);

Thank you.

Answer 1

It is a shorthand for an if statement.

$username = $_COOKIE['user'] ?: getusername($_COOKIE['user']);

Is the same as

if( $_COOKIE['user'] ) 
{
    $username = $_COOKIE['user'];
} 
else
{
    $username = getusername($_COOKIE['user']); 
}

see test suite here: https://3v4l.org/6XMc4

But in this example, the function 'getusername' probably doesn't work correct, because it hits the else only when $_COOKIE['user'] is empty. So, the parameter inside getusername() is also kind of empty.

Answer 2

It is short hand php, for example:

(true == true ? echo "this is true" : "this is false")

Written out this means:

if (true == true) {
    echo "This is true";
}
else {
    echo "This is false";
}

In your example, there is only an else statement.