php - Checking if already have the information in database -

i need check if register i'm trying insert on database, code isn't working, can me? code check:

 $query1 = sqlsrv_num_rows(sqlsrv_query("select * carro placa = '$placa'"));     if ($query1 == 1) {         echo "<script>alert('usuario já existe.'); history.back();</script>";     } 

you didn't pass connection object sqlsrv_query, query not running:-

$query1 = sqlsrv_num_rows(sqlsrv_query($your_database_connection_object_variable,"select * carro placa = '$placa'")); // provide data base connection object first parameter     if (count($query1) >= 1) {         echo "<script>alert('usuario já existe.'); history.back();</script>";     } 

note:- astonished code not raising error you.