www-data@5c2174446320:~/html$ php -i | grep -E 'mongodb|libmongoc|libbson'
Cannot load Xdebug - it was already loaded
/usr/local/etc/php/conf.d/mongodb.ini,
mongodb
libbson bundled version => 1.28.1
libmongoc bundled version => 1.28.1
libmongoc SSL => enabled
libmongoc SSL library => OpenSSL
libmongoc crypto => enabled
libmongoc crypto library => libcrypto
libmongoc crypto system profile => disabled
libmongoc SASL => enabled
libmongoc SRV => enabled
libmongoc compression => enabled
libmongoc compression snappy => enabled
libmongoc compression zlib => enabled
libmongoc compression zstd => enabled
libmongocrypt bundled version => 1.11.0
libmongocrypt crypto => enabled
libmongocrypt crypto library => libcrypto
mongodb.debug => no value => no value

<?php
namespace App\Models;
class ObjectIdTestModel extends \MongoDB\Laravel\Eloquent\Model
{
}

\dump();
// Uncommenting following line fixes the test
//gc_disable();
$objectId1 = new ObjectId();
$objectId2 = new ObjectId();
// Here we see public property "oid"
echo 'objectId1: ';
xdebug_debug_zval('objectId1');
echo 'objectId2: ';
xdebug_debug_zval('objectId2');
// Check possible assumption about iterating
$is_traversable = ($objectId1 instanceof \Traversable);
echo 'is_traversable: ' . var_export($is_traversable, true) . "\n";
// Check there are no properties for iterating in foreach hence there is not property "oid"
$reflect = new \ReflectionClass($objectId1);
$properties = $reflect->getProperties();
echo 'properties: ' . print_r($properties, true);
// Allocate a lot of objects
for ($i = 0; $i < 200; $i++) {
 $model = new ObjectIdTestModel();
 $model->save();
}
$a = ObjectIdTestModel::all();
// First foreach over \MongoDB\BSON\ObjectId
$number1 = 0;
foreach ($objectId1 as $key => $value) {
 $number1 += 1;
}
// Allocate a lot of objects again
$a = ObjectIdTestModel::all();
// Second foreach over \MongoDB\BSON\ObjectId
$number2 = 0;
foreach ($objectId2 as $key => $value) {
 $number2 += 1;
}
echo 'objectId1: ';
xdebug_debug_zval('objectId1');
echo 'objectId2: ';
xdebug_debug_zval('objectId2');
$this->assertEquals(1, $number1, 'number1');
$this->assertEquals(1, $number2, 'number2');

objectId1: objectId1: (refcount=1, is_ref=0)=class MongoDB\BSON\ObjectId { public $oid = (refcount=1, is_ref=0)='679a97b2d1cc47db6503f004' }
objectId2: objectId2: (refcount=1, is_ref=0)=class MongoDB\BSON\ObjectId { public $oid = (refcount=1, is_ref=0)='679a97b2d1cc47db6503f005' }
is_traversable: false
properties: Array
(
)
objectId1: objectId1: (refcount=1, is_ref=0)=class MongoDB\BSON\ObjectId { public $oid = (refcount=1, is_ref=0)='679a97b2d1cc47db6503f004' }
objectId2: objectId2: (refcount=1, is_ref=0)=class MongoDB\BSON\ObjectId { public $oid = (refcount=1, is_ref=0)='679a97b2d1cc47db6503f005' }
...
 number2
 Failed asserting that 0 matches expected 1.