Webpage logon problems

The library management system built on php is connected to the database. However, when logging on to the webpage, the system always prompts "incorrect administrator name". what is the problem? In fact, there is no error in the administrator's name and password. print the SQL statement and execute it in the queryserver to check whether the include (& quot; conn/conn. php & quot; web page login problem occurs.
The library management system made of php is connected to the database. However, when logging on to the webpage, the system always prompts "incorrect administrator name". what is the problem? In fact, there is no error in the administrator name and password.

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Print the SQL statement and execute it in the queryer.
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Discussion
Include ("conn/conn. php"); // connect to the data source
$ SQL = mysql_query ("select * from tb_manager where name = '". $ this-> name. "'and pwd = '". $ this-> pwd. "'", $ conn );
$ Info = mysql_fetch_array ($ SQL); // Retrieve the administrator name and password
If ($ info = false) {// if the administrator name or password is incorrect, a prompt is displayed.
Echo"