NULL MySQL转换为PHP PDO

Question

I'm looking for and don't find what's the value in PHP of NULL from MySQL got with PDO.
I found about PDO::PARAM_NULL but it's to insert data in MySQL and about constants PDO::NULL_NATURAL , PDO::NULL_EMPTY_STRING & PDO::NULL_TO_STRING but not about what's it for.
Example of code:

class CountryManager{
    public function getAll() {
        $countries = [ ];

        $query = $this->_db->query ( "SELECT f_id, f_icon, f_name FROM t_country ORDER BY f_name;" );

        while ( $data = $query->fetch ( PDO::FETCH_ASSOC ) )
            $countries [] = new CountryObject ( $data );

        return $countries;
    }
}

With CountryObject

class CountryObject {
    private $_f_id;
    private $_f_icon = null;
    private $_f_name;
}

I need to know if the nullable field f_icon is filled or not, and for all my nullable fields in my db as well.

Answer 1

The value in PHP of NULL from MySQL you get with PDO is null .

I suppose you are just instantiating your object wrong way. Let me suggest you my article, Fetching objects with PDO , which can prove thatboth PDO and mysql always return nulls all right:

class CountryObject {
    private $_f_id;
    private $_f_icon = null;
    private $_f_name;
}
$obj = $pdo->query("SELECT 1 as _f_id, null as _f_icon, 'name' as _f_name")
           ->fetchObject('CountryObject');
var_dump($obj);

returns

object(CountryObject)#4 (3) {
  ["_f_id":"CountryObject":private]=>
  string(1) "1"
  ["_f_icon":"CountryObject":private]=>
  NULL
  ["_f_name":"CountryObject":private]=>
  string(4) "name"
}