For your code user has to give name and as well as city to search.
If you want to search only by name then try below query code
$sql = "select * from missinginfo where mfname like '%$name%' or mlname like '%$name%' ";
Or you want to search by only city then try below code
$sql="select * from missinginfo where city like '%$missfrom%' ";
If you want to search by anyone of name or city you can try below code
$sql = "select * from missinginfo where mfname like '%$name%' or mlname like '%$name%' or city like '%missform%'";