从数据库返回计数

$DBH = new PDO( \"mysql:host=localhost;dbname=database_name\", \"user\", \"pass\" );
$DBH -> setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );

$STH = $DBH -> prepare( \"select count( users_id ) from table1 where username = :username\" );

$STH -> bindParam( \':username\', $_POST[\'username\'], PDO::PARAM_STR, 100 );

$STH -> execute();

$strCount = $STH -> rowCount();

if( $strCount == 1 ) {
    echo $strCount;
    echo \"user has already registered, do nothing\";
} elseif ( $strCount == 0 ) {
    echo $strCount;
    echo \"user has not registered, insert into db\";
} else {
    echo $strCount;
    echo \"something is wrong, should only ever be 0 or 1\";
}