Get the title before comma

I am using this code to return the title of the post on a gravity form field.

add_filter('gform_field_value_page_name', 'page_name_filler');
    function page_name_filler($value){
        return get_the_title() ; 
    }

However, usually the title of the post is too long and it overfills the field. Hence I would only like to retain the first portion of the title before a comma “,” if it exists on the title. Usually I will have multiple commas on my titles.

If a comma doesn’t exist then the full title should be displayed.

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