MySQLi Numrows Errors

All;

I have the code:
#1      $sql_str        =   "SELECT * FROM mydb.mytab WHERE `field` LIKE '%swomething%';";
#2      $dbc            =   new mysqli('localhost','mydb','mypass','mydb') or die(mysqli_error());
#3      $dbc_res        =   $dbc->query ( $sql_str );
#4      $qry_nrs        =   $dbc_res::$num_rows ( $dbc_res );
#5      $qry_nrs        =   $dbc_res->$num_rows ( $dbc_res );
#6      $qry_nrs        =   mysqli_num_rows ( $dbc_res );
#7      $qry_nrs        =   $dbc_res::$num_rows;
#8      $qry_nrs        =   $dbc_res->$num_rows;
I've tried all five methods lines #4-8 and none work, but this is syntax from PHP manual, so what am I not percieving and therefore doing wrong?

Cheers!

TBNK

OK!

var_dump results:

object(mysqli_result)#3 (5) {
  ["current_field"]=>
  int(0)
  ["field_count"]=>
  int(6)
  ["lengths"]=>
  NULL
  ["num_rows"]=>
  int(0)
  ["type"]=>
  int(0)
}

This is a test for existing data row so since nothing in the DB.Table NULL is the correct response.

Now assuming the error is that it can't handle the NULL.

What is the right code for handling the NULL?

Cheers!

TBNK