class Classy
{
    /** @var string[] */
    public $prop = array();
}

aop_add_before("write in Classy->prop", function(AopJoinpoint $joinpoint) {
    echo "someone writes into " . $joinpoint->getPropertyName()
    . " keys " . print_r($joinpoint->getPropertyKeys(), true)
    . " value " . $joinpoint->getAssignedValue()
});

$object = new Classy();
$object->prop["michel"]["rouge"] = "is classy";

// Would display :
// someone writes into prop keys array(0 => michel, 1 => rouge) value is classy