GetOne? Sometimes the failure resolution method

GetOne? Sometimes it fails.

PHP Code

  
  function Getmaxlevel ($model)    {         $sql = "Select Max (slevel) from boxfile                 where model = ' $model '";             $record _nums = $this->db->getone ($sql);           Print_r ($record _nums);        return $record _nums;         }

Why does my function occasionally fail? I just returned the biggest, and then I didn't return the biggest. I feel like I haven't changed anything.

------Solution--------------------
Do you see how the parameters are passed in the same way that they are called when they are invalid or valid?

------Solution--------------------
You're worth the package, so it's hard to see the problem.
You have to look at the specific wording of the getone, whether it's returning a resource, an int, or something else.
------Solution--------------------
Your own humble sentence output to see

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