What is a double question mark in PHP?

@audrey.hodkiewicz The double question marks are short syntax for the isset() function and the quickest way to check if a variable exists is to use the value, otherwise some default value. Look into the code as an example in PHP below:

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<?php

$name = $username ?? 'unknown';

// Output: unknown
echo $name;

// Equivalent to
$name = isset($username) ? $username : 'unknown';

// Output: unknown
echo $name;

@audrey.hodkiewicz 

In the example above, the double question mark operator checks if the variable $username exists. If it does, it assigns its value to the $name variable. If it does not exist, it assigns the value 'unknown' to the $name variable. The double question mark operator in this context is a shorthand way of using the isset() function along with the ternary operator.