Output values of the array only if not empty or null

I am really new to php and do not know what I should look up to get this solved. I am trying to show only the values if the variable is not empty nor null.

Within an array I assign:

$attributes [
'glutenfree'               => getPublicClassificationsDescription($classifications, ARTICLE_GLUTENFREE),
            'lactosefree'              => getPublicClassificationsDescription($classifications, ARTICLE_LACTOSEFREE),
            'flavouringfree'           => getPublicClassificationsDescription($classifications, ARTICLE_FLAVOURINGFREE),
            'corerange'                => getPublicClassificationsDescription($classifications, ARTICLE_CORERANGE),
            'engro'                    => getPublicClassificationsDescription($classifications, ARTICLE_ENGRO),
            'vegan'                    => getPublicClassificationsDescription($classifications, ARTICLE_VEGAN),
...
];

and a lot of other attributes more. I want the output that it is only printed to the CSV if it is not empty nor null.

Right now I get the result like this:

glutenfree=,lactosefree=,flavouringfree=,corerange=,engro=,vegan=No,...

The output I need is like everything that is empty/null should be gone but the ones with value should be there. In this example:

vegan=No,...

For example if I try with "empty" or "isset" it does not work and I get a blank page with no errors.

$glutenfree = getPublicClassificationsDescription($classifications, ARTICLE_GLUTENFREE);

$attributes [
 if (!empty($glutenfree)) {
                'glutenfree'          => $glutenfree,
                'lactosefree'              => getPublicClassificationsDescription($classifications, ARTICLE_LACTOSEFREE),
                'flavouringfree'           => getPublicClassificationsDescription($classifications, ARTICLE_FLAVOURINGFREE),
                'corerange'                => getPublicClassificationsDescription($classifications, ARTICLE_CORERANGE),
                'engro'                    => getPublicClassificationsDescription($classifications, ARTICLE_ENGRO),
                'vegan'                    => getPublicClassificationsDescription($classifications, ARTICLE_VEGAN),
    ...
    ];