PHP PDO提取不起作用？

Question

I can successfully select an object, but I cannot fetch all rows from the database using the following code, can anyone see any obvious errors?

    $sql2 = "SELECT ID, Latitude, Longitude, Name FROM Countries";
    $stmt2 = $pdo->prepare($sql2);
    $stmt2->execute();

    while ($row = $stmt2->fetch(PDO::FETCH_ASSOC)) {
        echo $countryID = $row->ID;
        echo $countryName= $row->Name;
        echo $longitude2 = $row->Longitude;
        echo $latitude2 = $row->Latitude;
    }

Answer 1

The parameter PDO::FETCH_ASSOC tells PDO to return the result as an associative array. SO you can fetch array not object

 while ($row = $stmt2->fetch(PDO::FETCH_ASSOC)) {
        echo $countryID = $row['ID'];
        echo $countryName= $row['Name'];
         //Rest of the code

    }

Answer 2

You have to realize that PDO::FETCH constants are on purpose. And if you want to use object notation, you have to specify PDO::FETCH_OBJ instead of ...ASSOC .

Anyway, PDO::FETCH_LAZY should be most preferred way, as it will let you use ANY notation:

while ($row = $stmt2->fetch(PDO::FETCH_LAZY)) {
    echo $row->ID;    // all
    echo $row['ID'];  // three
    echo $row[0];     // works
}

with even less memory overhead than any other method. With no memory overhead at all, to be exact.