Hướng dẫn check object empty php

Edit: I didn't realize they wanted to specifically check if a SimpleXMLElement object is empty. I left the old answer below

Updated Answer [SimpleXMLElement]:

For SimpleXMLElement:

If by empty you mean has no properties:

$obj = simplexml_load_file[$url];
if [ !$obj->count[] ]
{
    // no properties
}

OR

$obj = simplexml_load_file[$url];
if [ ![array]$obj ]
{
    // empty array
}

If SimpleXMLElement is one level deep, and by empty you actually mean that it only has properties PHP considers falsey [or no properties]:

$obj = simplexml_load_file[$url];
if [ !array_filter[[array]$obj] ]
{
    // all properties falsey or no properties at all
}

If SimpleXMLElement is more than one level deep, you can start by converting it to a pure array:

$obj = simplexml_load_file[$url];
// `json_decode[json_encode[$obj], TRUE]` can be slow because
// you're converting to and from a JSON string.
// I don't know another simple way to do a deep conversion from object to array
$array = json_decode[json_encode[$obj], TRUE];
if [ !array_filter[$array] ]
{
    // empty or all properties falsey
}

Old Answer [simple object]:

If you want to check if a simple object [type stdClass] is completely empty [no keys/values], you can do the following:

// $obj is type stdClass and we want to check if it's empty
if [ $obj == new stdClass[] ]
{
    echo "Object is empty"; // JSON: {}
}
else
{
    echo "Object has properties";
}

Source: //php.net/manual/en/language.oop5.object-comparison.php

Edit: added example

$one = new stdClass[];
$two = [object]array[];

var_dump[$one == new stdClass[]]; // TRUE
var_dump[$two == new stdClass[]]; // TRUE
var_dump[$one == $two]; // TRUE

$two->test = TRUE;
var_dump[$two == new stdClass[]]; // FALSE
var_dump[$one == $two]; // FALSE

$two->test = FALSE;
var_dump[$one == $two]; // FALSE

$two->test = NULL;
var_dump[$one == $two]; // FALSE

$two->test = TRUE;
$one->test = TRUE;
var_dump[$one == $two]; // TRUE

unset[$one->test, $two->test];
var_dump[$one == $two]; // TRUE