In PHP, one can assign a default value to a variable if it does not already exist using the null coalescing operator ??.
The syntax for using the null coalescing operator is
If the $value is set and not null, then the value of $value is assigned to $variable. If $value is not set or is null, then the value 'default' is assigned to $variable.
Example 1:
// Using null coalescing operator
$result = $name ?? 'Anonymous';
echo $result;//Output will be "Anonymous"
?>
Example 2:
// Using null coalescing operator
$result = $number ?? 0;
echo $result;//Output will be 5
?>
In the above examples, if $name is not set or is null, then the default value of 'Anonymous' will be assigned to $result. Similarly, if $number is set to 5, then the value of $number will be assigned to $result instead of the default value.