Session_Start related issues

Session_Start problems
Session_Start ();
echo fuck;
if ($_post[' Submit ']== ' Register ') {
Header (' Location:sign_in.php ');
}
$db =mysql_connect (' localhost ', ' bp6am ', ' 123 ') or Die (' Unable to connect. ');
mysql_select_db (' web ', $db) or Die (Mysql_error ($db));
if (!isset ($_session[' logged ')) | | $_session[' logged ']!=1) {
$query = ' Select user_name from user where user_name= ' '. $_post[' username '. ' " and password= "'. $_post[' password '). '";
$result =mysql_query ($query, $db) or Die (Mysql_error ($db));
if (mysql_num_rows ($result) ==1) {
echo fuck;
$_session[' username ']= $user _name;
$_session[' logged ']=1;
echo fuck;
Header (' Refresh:5; Location:index.php ');
}
else{
$_session[' username ']= ';
$_session[' logged ']=0;
Echo entered in a wrong the user name or password, please check. If you want to register, click here.;
}
}
?>
I set the Session_Start () at the beginning;
There is no output before this, but I am prompted with HTTP error (Internal Server error): An unexpected condition is encountered while the Server is Attem Pting to fulfill the request. If the session_start is correct, fuck should be able to be called out.
Ask for advice.
Another: This is my own writing login module, do not know if there is no security concerns?
Thank you

------Solution--------------------
Open PHP Error display function, you will see this line out of fatal error
Echo entered in a wrong the user name or password, please check. If you want to register, click here.;


Code Geek Recommended solutions:The server encountered an internal error (), prevented it from fulfilling this request.,http://www.daimami.com/java-we B/317.html

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