A simple recursive function in PHP doesn't work

Question

I'm trying to get a parent category for a given sub category using the following function in PHP.

    require_once("Connection.php");
    $flag=true;

    function get_parent_id($cat_id, $parent_id)
    {         
        if ($parent_id==0)
        { 
            return($cat_id);
        }
        else if ($flag==true)
        {                           
            $data1=mysql_query("select parent_id from category where cat_id=" + $cat_id);

            while($row = mysql_fetch_assoc($data1)) 
            {   
                $parent_id=$row['parent_id'];
            }
            $flag = false;                             
        }
        else if ($flag==false)
        {                
            $data2=mysql_query("select cat_id from category where cat_id=" + $parent_id);

            while($row = mysql_fetch_assoc($data2)) //The warning comes from here.
            {   
                $cat_id=$row['cat_id'];
            }                                                           
            $flag = true;            
        }           

        $cat_id = get_parent_id($cat_id, $parent_id);           
        return($cat_id);
    }   
}

echo get_parent_id($ed_id, $parent_id); //Call the above function.

It always prompts the following warning.

 Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL 
 result resource in C:\wamp\www\zoom\Category.php on line 492

Even though there is no error in SQL. The included file Connection.php also works fine on all other pages. I didn't understand at all why this happens.

Try replacing the $data2 query with "select cat_id from category where cat_id=$parent_id" If to no avail, echo/print the value of $data2 and make sure that it's formatted properly as a SELECT request. — Mike
– Mike, Commented Sep 30, 2012 at 0:52

Niet the Dark Absol · Accepted Answer · 2012-09-30 00:51:42Z

7

Strings are concatenated with ., not +.

String Operators

answered Sep 30, 2012 at 0:51

Niet the Dark Absol

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