SiteInvoice - invoices

Cause: A foreach loop is executed according to the following parameters:

foreach($array as $key => $value) { actions; }

If $array is empty/null, it results in a warning because a system simply cannot assign values to non-existing keys.

Solution: To fix these types of issues, a simple if loop has to be added before the foreach loop is executed to check whether or not $array is empty.

if ($array) { 
    foreach($array as $key => $value) { 
        actions; 
    } 
}

This means the foreach loop will be skipped altogether if $array is empty/null.