Unable to invoke database related issues

Unable to invoke database problem
I was under Ubuntu, with the eclipse pdt,conn.php used to link the database, the display was successful, so
Include ' conn.php ';
if ($_post[' submit '))
{

$sql = "INSERT into BBS (id,user,title,content,lastdate) VALUES (' ', ' $_post (user) ', ' $_post (title) ', ' $_post (content) ', Now ()) ";
mysql_query ($sql);
echo ' success ';
}
?>

A small form, input later, commit, show success, but why is there no information inserted in the database? Escorts .... Beginning to think that the SQL statement is wrong, so enter the SQL statement under phpMyAdmin, execute correctly. What's wrong??

------Solution--------------------
Could not be a version of the problem
Mysql_connect (...);
mysql_select_db (' database name ');
Is that how you use it?

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