A fudge would be to use null coalesce(??) to set it to an empty array if null...

if (count($this->implements??[]) > 0)

If var is not an array or an object with implemented Countable interface, 1 will be returned.

Ref: http://php.net/manual/en/function.count.php

The die() function behaves like exit(). This means that an Integer argument is considered as a "status".

From the doc:

If status is an integer, that value will be used as the exit status and not printed. Exit statuses should be in the range 0 to 254, the exit status 255 is reserved by PHP and shall not be used. The status 0 is used to terminate the program successfully.

If you want to print a value, I recommend you to use something else like echo, print_r, etc.

Do you have the same troubles without using die() ?

You can use array_filter to only keep the values that are “truthy” in the array, like this:

array_filter($array);

If you explicitly want only non-empty, or if your filter function is more complex:

array_filter($array, function($x) { return !empty($x); });
# function(){} only works in in php >5.3, otherwise use create_function

So, to count only non-empty items, the same way as if you called empty(item) on each of them:

count(array_filter($array, function($x) { return !empty($x); }));

However, as empty() is only a shorthand for 'variable is set and the value is truthy', you don't really gain anything from that, because if your array contains values such as FALSE or "0", those would count as empty as well, same as with the plain call to array_filter.

The better way is to be explicit about what you want to count, e.g. if you want to exclude empty strings only, then use:

array_filter($array, function($x) { return ($x !== ""); });