mysql副本表不起作用

Question

I'm using PHP to copy table for backup.

Code is simple.

///////////////////////////////////////////////////////////////
                //  BACKUP TABLE
///////////////////////////////////////////////////////////////
mysqli_query($conn, "DROP TABLE SerialTable3");
mysqli_query($conn, "CREATE TABLE SerialTable3 LIKE SerialTable2");
mysqli_query($conn, "INSERT INTO SerialTable3 (SELECT * FROM SerialTable2)");

mysqli_query($conn, "DROP TABLE SerialTable2");
mysqli_query($conn, "CREATE TABLE SerialTable2 LIKE SerialTable1");
mysqli_query($conn, "INSERT INTO SerialTable2 (SELECT * FROM SerialTable1)");

mysqli_query($conn, "DROP TABLE SerialTable1");
mysqli_query($conn, "CREATE TABLE SerialTable1 LIKE SerialTable");
mysqli_query($conn, "INSERT INTO SerialTable1 (SELECT * FROM SerialTable)");
///////////////////////////////////////////////////////////////

Drop table works as I confirm. Create Table also works.

But Insert SQL doesn't work... I saw a lot of other people doing this to copy table. But in my case, never works...

I know it's all same but I tried

mysqli_query($conn, "INSERT INTO SerialTable1 SELECT * FROM SerialTable");
mysqli_query($conn, "INSERT INTO SerialTable1 AS SELECT * FROM SerialTable");
mysqli_query($conn, "INSERT INTO SerialTable1 AS (SELECT * FROM SerialTable)");

What's wrong? As dropping and creating works, connection has no problem too.