当我直接将查询放入数据库时，查询工作正常，但不是通过PHP的查询

这是我输入数据库的查询。我的mysql数据库是UTC，但我的数据输入到美国东部

SET time_zone = '-6:00';
SELECT HOUR(created_at), count(*) AS sent
FROM tweets
WHERE created_at
BETWEEN CURDATE()
AND NOW()
GROUP BY HOUR(created_at)
ORDER BY HOUR(created_at)

我的php看起来像：

$q = "SET time_zone = '-6:00'; 
SELECT HOUR(created_at), count(*) AS sent FROM tweets
WHERE created_at
BETWEEN CURDATE()
AND NOW()
GROUP BY HOUR(created_at)
ORDER BY HOUR(created_at)";

$r = @mysqli_query ($dbc, $q);

while ($row = mysqli_fetch_array($r, MYSQLI_ASSOC)) {

echo "[".$row['HOUR(created_at)'].",".$row['sent']."],";

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是否有任何原因使直接插入数据库工作正常并返回结果，而php根本不工作。

您不能同时运行两个查询如何设置它工作：/php/mysql新增功能。您需要使用multi_query一次运行两个查询。