Propel - get primary key after find - php

Question

The question boils down to finding the proper way how to getPrimaryKey when iterating over a yielded result. When using select method, the result is an object of ArrayCollection which doesn't provide the getPrimaryKey method. A simple snippet
$q = UserQuery::create();
$q->select('a', 'b'); //yields an ArrayCollection object, doesn't have getPrimaryKey method when iterated
$q->find();
However,
$q = UserQuery::create();
$q->find(); //yields an ObjectCollection object, has getPrimaryKey method when iterated
Update
I have tried to use the setFormater to force using the ObjectCollection. Ultimately, it resulted in exception being thrown.
$q = UserQuery::create()
->setFormater(ModelCriteria::FORMAT_OBJECT)
->select('a', 'b')
->find(); //Error populating object
Update 2
Providing an exact use case, since it may be unclear at first what I am looking for. I have a table with >100 columns. I am providing the functionality using behaviour to not disable (not select) some of them. Thus, I am unseting some of the columns, and basing the $q->select on the remaining ones.
if (!empty($tableQuery->tableColumnsDisable)) {
$columns = $tableQuery->getTableMap()->getColumns();
foreach ($columns as $index => $column) {
if (!empty($tableQuery->tableColumnsDisable[$column->getName()])) {
unset($columns[$index]);
continue;
}
$columns[$index] = $column->getName();
}
//TODO - returns array collection, object collection needed
$tableQuery->select($columns);
}

Answer 1

When using select(), Propel will skip object hydration and will just return an ArrayCollection containing an array for each result row.
To retrieve the id of each result row, you need to add the column name to the select(). You can then just retrieve the value from the row arrays by using the column name:
$users = UserQuery::create()
->select(['id', 'a', 'b'])
->orderBy('c')
->find();
foreach ($users as $user) {
$id = $user['id'];
}
The select functionality is described in the documentation and in the docblock of Propel\Runtime\ActiveQuery\ModelCriteria#select() (source).
When you are using Propel 1, the functionality is the same. Read more about it in the Propel 1 documentation or the docblock of ModelCriteria#select() (source).