Note:  If replacement is not an array, it will be typecast to one (i.e. (array) $parameter). This may result in unexpected behavior when using an object replacement .  

Example :

<?php
class A()
{
    private $a;
    private $b;
    public function __construct()
    {
        $this->a = "foo";
        $this->b = "bar";
    }
}

$array = array();
array_splice($array, 0, 0, new A());
print_r($array);
?>

Outputs :

Array : Array
{
    [0] => foo
    [1] => bar
}

Solution : Enforce the array() on the object.

<?php
array_splice($array, 0, 0, array(new Object());
?>

Source : http://bugs.php.net/bug.php?id=44485