Html login jumps to the php page to connect to the database, prompting that the submission is not successful

The html login jumps to the php page to connect to the database and prompts that the submission is unsuccessful. this is the form in HTML:






This is the php login connection database php:
If (isset ($ _ POST ["submit"]) & $ _ POST ["submit"] = "login ")
{
$ User = $ _ POST ["username"];
$ Psw = $ _ POST ["password"];
If ($ user = "" | $ psw = "")
{
Echo "script" alert ('Enter your username or password! '); History. go (-1); script ";
}
Else
{
$ Con = mysql_connect ("Wagner. 0.0.1", "root", "1234 ");
If (! $ Con)
{
Die ('could not connect: '. mysql_error ());
}
Mysql_select_db ("vote ");
Mysql_query ("set names 'utf-8 '");
$ SQL = "select username from password table where username = '$ _ POST [username]' and password = '$ _ POST [password]'";
$ Result = mysql_query ($ SQL );
If ($ result)
{
Echo $ username, 'Welcome! Go to User Center
';
}
Else
{
Echo "script alert ('The user name or password is incorrect! '); History. go (-1); script ";
}
}
}
Else
{
Echo "script alert ('submission failed! '); History. go (-1); script ";
}
?>

Reply to discussion (solution)

Isset ($ _ POST ["submit"])
This phpif condition is empty and does not enter the php program. but isn't it passed a value in form?

Print $ _ POST ["submit"] to see what it is.

The form cannot be submitted. change the button to input.

$ _ POST ["submit"] = "login"
When the form and handler are not in the same file, there is a certain risk of such judgment.
The encoding of the two files must be consistent!

$ _ POST ["submit"] = "login"

Print $ _ POST ["submit"] to see what it is.

Is it useless to change to input?

I don't know what's going on. it's successful... Thank you!