I want to count all the rows for todays / yesterdays date based on a DATETIME - mysql+php
You need to access column by index :

if ( $nt = mysql_fetch_array($q)){
echo $nt[0];
}


(Note if instead of while - it's not required, but your query returns at most 1 row, so no need for while).
If you want to access column by name, change the query to use aliases:

$q=mysql_query(" SELECT COUNT(*) AS total_number FROM menjava 
WHERE date_submitted &gt;= DATE_SUB(CURRENT_DATE(), INTERVAL 1 DAY)",$link2);
// now you can 
if ( $nt = mysql_fetch_array($q)){
echo $nt["total_number"];
}


Also, while debugging it makes sense to output errors if any :

$q=mysql_query(....) or die(mysql_error());