https://3v4l.org/7qdmA

traits_test.php

<?php

trait base_trait
{
    protected $prop = [];

    function __construct()
    {
        var_dump($this->prop);
    }
}

class base_class
{
    use base_trait;
}

class test_class_property
    extends base_class
{
    protected $prop = ['a' => 'b'];
}

trait overlay_trait
{
    protected $prop = ['a' => 'b'];
}

class test_class_overlay
    extends base_class
{
    use overlay_trait;
}

new base_class;
new test_class_property;
new test_class_overlay;