$ conn-> query（...）的结果可能不为null且有0条记录

Question

I came across the following in some old PHP code that I have to work on. My question is, are both those Ifs required? In other words, if a result is returned it must have returned greater than zero records, right? And the converse - meaning if $result is False, can I assume that no records have been found?

$sql = "SELECT * FROM houses WHERE ownerphone=$pn";
$result = $conn->query($sql);
if ($result) {
    $count = $result->num_rows;
    if ($count > 0){
       ....Stuff happens here...
    } else {
        ...What happens here?...
    }
} else {
     ...Other Stuff happens here
}

Answer 1

Yes, both are required.

if a result is returned it must have returned greater than zero records, right?

Wrong.

If you don't get a result then you got an error and you won't have an object to read the number of results back from.

You can get zero rows back from a successful request.

if $result is False, can I assume that no records have been found?

Well, yes. Sort of. That's why the if statement stops you checking to see if there are a number of rows if the result is False.

… but not getting rows back because there was an error is different to not getting rows back because there were none to find.