When unsetting elements as you go it will not remove the second index of the Array being worked on. Im not sure exactly why but there is some speculations that when calling unsetOffset(); it resets the pointer aswell.
<?php
$a = new ArrayObject( range( 0,9 ) );
$b = new ArrayIterator( $a );
for ( $b->rewind(); $b->valid(); $b->next() )
{
echo "#{$b->key()} - {$b->current()} - \r\n";
$b->offsetUnset( $b->key() );
}
?>
To avoid this bug you can call offsetUnset in the for loop
<?php
for ( $b->rewind(); $b->valid(); $b->offsetUnset( $b->key() ) )
{
?>
Or unset it directly in the ArrayObject
<?php
$a->offsetUnset( $b->key() );
?>
which will produce correct results
