Basic Understanding Needed: PHP MySQLi Row Navigation - php

Question

I'm using PHP and MySQLi and following a tutorial-type example and have some basic behavioral questions. A php code sample follows (hm, hope I format it correctly, 1st post here):
<?php
$db = new mysqli('hostLiteral', 'userLiteral', 'passwordLiteral', 'people');
$results = $db->query("SELECT * FROM people")
if($results->num_rows) {
while($row = $results->fetch_object()) {
$records[] = $row;
}
$results->free();
}
?>
I used a DBMS many, many years ago and perhaps it's that behavior that's keeping me from understanding this.
My perception is that when the 'SELECT * FROM people' is executed, MySQL would scan the entire database, get all the pertinent data, and end up 'pointing' at the last record in the database. So when the 'while' loop begins, I would think that's where it's starting, it would only get the last record or row and be done.
But even if it did somehow start at the top of the database at the first row, how does it know to move through the database unless 'fetch_object()' is somehow telling it to move to the next row?
I'm certain I'm missing basic SQL behavior here. But I've not found a good explanation to dispel these concepts that were placed in my head years back.
Thanks for any aid in understanding!

Answer 1

The query leaves the cursor pointing at the first row of your result set rather than the last. Since the general use case is to move forward through the rows, it would make little sense to leave the cursor at the last row.
In addition, fetch_object does exactly what you surmise. It gets the current row and advances the cursor to the next row. It's interesting that the documentation doesn't state that explicitly (like it does with fetch_row, but the example given makes it clear enough that that's what it does:
/* fetch associative array */
while ($obj = mysqli_fetch_object($result)) {
printf ("%s (%s)\n", $obj->Name, $obj->CountryCode);
}