Use the object returned by simplexml_load_string($xml_str) to access non-existent attributes, empty is true

<code>$xml_str = <<<EOT
    <xml>
        <fee_type><![CDATA[CNY]]></fee_type>
        <return_code><![CDATA[SUCCESS]]></return_code>
        <trade_type><![CDATA[NATIVE]]></trade_type>
    </xml>
EOT;
$obj = simplexml_load_string($xml_str);
var_dump($obj->game);
if(empty($obj->game)) {
    echo '空的';
} else {
    echo "不空";
}
</code>

The game attribute does not exist, but var_dump has results. Why?

Reply content:

<code>$xml_str = <<<EOT
    <xml>
        <fee_type><![CDATA[CNY]]></fee_type>
        <return_code><![CDATA[SUCCESS]]></return_code>
        <trade_type><![CDATA[NATIVE]]></trade_type>
    </xml>
EOT;
$obj = simplexml_load_string($xml_str);
var_dump($obj->game);
if(empty($obj->game)) {
    echo '空的';
} else {
    echo "不空";
}
</code>

The game attribute does not exist, but var_dump has results. Why?

Although the game attribute does not exist, when directly obtaining this attribute, the magic method __get() of SimpleXMLElement will be called. This method returns an empty object and is printed out by var_dump.
But the object should be true when empty() is judged. Why is it false here?
Because empty() is not equal to a direct Boolean judgment, but empty($var) === isset($var) && $var, so the magic method __isset( of SimpleXMLElement will be called first) ), and __isset() returns that this attribute does not exist, and the following __get() is automatically skipped.

Because simplexmlelement internally implements setter and getter, just like the magic methods __set() and __get(),