MySQL integer field is returned as string in PHP

Easiest Solution I found:

You can force json_encode to use actual numbers for values that look like numbers:

json_encode($data, JSON_NUMERIC_CHECK) 

(since PHP 5.3.3).

Or you could just cast your ID to an int.

$row = $result->fetch_assoc();
$id = (int) $row['userid'];

When you select data from a MySQL database using PHP the datatype will always be converted to a string. You can convert it back to an integer using the following code:

$id = (int) $row['userid'];

Or by using the function intval():

$id = intval($row['userid']);

Use the mysqlnd (native driver) for php.

If you're on Ubuntu:

sudo apt-get install php5-mysqlnd
sudo service apache2 restart

If you're on Centos:

sudo yum install php-mysqlnd
sudo service httpd restart

The native driver returns integer types appropriately.

As @Jeroen has pointed out, this method will only work out-of-the-box for PDO.
As @LarsMoelleken has pointed out, this method will work with mysqli if you also set the MYSQLI_OPT_INT_AND_FLOAT_NATIVE option to true.

Example:

$mysqli->options(MYSQLI_OPT_INT_AND_FLOAT_NATIVE, TRUE);