如何知道insert .. select是否确实插入了任何行？

Here is my code:

$stm = $dbh
->prepare("INSERT INTO resend_pass(user_id, token, date_time)
            SELECT ?, ?, unix_timestamp()
            FROM dual
            WHERE NOT EXISTS( SELECT count(*) AS num_week,
                                     COALESCE(sum(date_time > unix_timestamp(DATE_SUB(now(), INTERVAL 1  day))),0)  as num_day,
                                     COALESCE(sum(date_time > unix_timestamp(DATE_SUB(now(), INTERVAL 1  hour))),0) as num_hour,
                                     COALESCE(sum(date_time > unix_timestamp(DATE_SUB(now(), INTERVAL 1 minute))),0) as num_1min
                                  FROM resend_pass
                                 WHERE user_id   = ?  
                                   AND date_time > unix_timestamp(DATE_SUB(now(), INTERVAL 1 WEEK))
                                HAVING num_week > 11 OR num_day > 5 OR num_hour > 3 OR num_1min > 0 );");

if($stm->execute(array(10, 'token', 10))){
    echo 'inserted';
} else {
    echo 'failed';
}

My script always prints inserted, even when no row inserted. Why? And how can I fix it?

Noted that I've used this approach to know if it inserted successfully.

INSERT ... SELECT is considered successful when it INSERTs all the rows returned by SELECT; if the SELECT returns zero rows then the statement will successfully insert zero rows.

To determine if rows have been inserted, one has to test the number of affected rows; with PDO this is done by querying the `PDOStatement::rowCount() method, something like this:

try {
    $stm = $dbh->prepare("INSERT .. SELECT query");
    $stm->execute();
    if ( $stm->rowCount() > 0 ) {
        echo 'inserted';
    } else {
        throw new Exception('No rows inserted');
    }
} catch(Exception $e) { 
    echo $e;
}

execute returns false only if there was an error. Your script echoes 'inserted' because there was no error. In short, your query was run successfully. Nothing was inserted because no record met the conditions in your SQL's WHERE clause

If you need to know whether a row was actually inserted, call the rowCount() function instead:

if($stm->execute(...)===false):
    //there was an error
elseif($stm->rowCount()<1): // $stm->affected_rows if you use MySQLi
    //no row was inserted
else:
    //at least one row was inserted
endif

Documentation here.

How about using the function mysqli_affected_rows() http://php.net/manual/es/mysqli.affected-rows.php

If you are using PDO (I think is your case) you may want to try $stm->rowCount().

Prepared statements will return the number of affected rows via that method.