MySQL问题：不正确的整数值：第1列的''

Question

For the following sql statements (inside of php):

$sql = "CREATE TABLE {$value}_GAMES ( ".  // Creating a new table for each team
    "nfl_game_id INT NOT NULL, ".
    "team VARCHAR(3) NOT NULL, ".
    "opponent VARCHAR(3) NOT NULL, ".
    "totfd INT NOT NULL, ".
    "totyds INT NOT NULL, ".
    "pyds INT NOT NULL, ".
    "ryds INT NOT NULL, ".
    "pen INT NOT NULL, ".
    "penyds INT NOT NULL, ".
    "trnovr INT NOT NULL, ".
    "pt INT NOT NULL, ".
    "ptyds INT NOT NULL, ".
    "ptavg INT NOT NULL, ".
    "PRIMARY KEY ( nfl_game_id ));";

$retval = mysql_query($sql, $con); // Execute SQL Code
if(! $retval)
{
die('Could not create table: ' . mysql_error());

$sql = "INSERT INTO {$value}_GAMES(nfl_game_id, team, opponent, totfd, ".
"totyds, pyds, ryds, pen, penyds, trnovr, pt, ptyds, ptavg)".
"VALUES('$game', '$team', '$opponent', '$totfirstdown', '$totyds',".
"'$pyds', '$ryds', '$pen', '$penyds', '$trnovr', '$pt', '$ptyds', ".
"'$ptavg')";
$ret_val = mysql_query($sql,$con); // Execute SQL Code
if(! $ret_val)
{
    die('Could not add JSON data to table: ' . mysql_error());
}

I'm getting the following error:

Could not add JSON data to table: Incorrect integer value: '' for column 'nfl_game_id' at row 1

When I echo the API call, this is what the data looks like:

[{"nfl_game_id":2009081350,"team":"ARI","opponent":"PIT","totfd":22,"totyds":329‌​,"pyds":259,"ryds":70,"pen":4,"penyds":27,"trnovr":2,"pt":6,"ptyds":266,"ptavg":3‌​7}, .....

Any idea what's going on?