php使用mysql_connect、mysqli和pdo连接mysql返回的数据都是字符串格式

1. 使用mysql_connect()

error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED);
$con = mysql_connect("127.0.0.1","root","root");
if (!$con)
{
    die('Could not connect: ' . mysql_error());
}
mysql_select_db("test", $con);
$result = mysql_query("SELECT * FROM test_oo");

while($row = mysql_fetch_array($result))
{
    // echo gettype($row['id']) . "--" . gettype($row['smallint']);
    echo "<br />";
    var_dump($row['id']);
    if(is_int($row['id']))
    {
        echo 'int';
    }elseif(is_string($row['id']))
    {
        echo 'string';
    }
}

2. 使用mysqli

$con=mysqli_connect("localhost","root","root","test"); 
// 检查连接 
if (!$con) 
{ 
    die("连接错误: " . mysqli_connect_error()); 
} 
$result = mysqli_query($con,'select * from test_oo');
$arr = mysqli_fetch_array($result,MYSQLI_ASSOC);
var_dump($arr);

3. 使用pdo

error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED);
$user = 'root';
$pass = 'root';
try {
    $dbh = new PDO('mysql:host=localhost;dbname=test', $user, $pass);
    foreach($dbh->query('SELECT * from test_oo') as $row) {
        print_r($row);
        echo '<br>';
        settype($row['id'],'int');
        echo gettype($row['id']);
        echo '<br>';
    }
    $dbh = null;
} catch (PDOException $e) {
    print "Error!: " . $e->getMessage() . "<br/>";
    die();
}