Do I understand that your database has multiple columns and your query was a multiple-column query, like "SELECT source_mail,hostname,machine_name FROM ..."?
If that's the case then,

$db->FetchRow()
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is just returning one single value from the columns returned and using

@hydra_data ->FetchRow_Array()
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instead will put each column's value in a separate element of @hydra_data, then you won't have to split yourself.