Notes for SimpleXML

SimpleXML provides a simple and fast XML operation method, greatly improving the efficiency of XML operations. But sometimes it may cause a lot of trouble if you are not careful. Check the following code:

$ Xml = simplexml_load_string (<root> <title> title </title> </root> );

$ Title = $ xml-> title;

Echo $ title;

$ Xml-> title = test;

Echo $ title;
 

Guess what the second output result will be? It is test, not the title in imagination. Why? The reason is as follows:

Echo gettype ($ xml-> title) // object

Echo get_class ($ xml-> title); // SimpleXMLElement
 

Can you see that $ xml-> title is an instance of the SimpleXMLElement class, not a string. Therefore, $ title actually stores a reference to the SimpleXMLElement class, rather than a copy of the string. To obtain a copy of a string, you can only perform type conversion:

$ Title = (string) $ xml-> title; // obtain the string

$ Xml-> title = test;

Echo $ title; // output title
 

SimpleXMLElement should implement an interface similar to _ tostring () (if you are interested, check the PHP source code in "ext/simplexml ), can be expressed in expressions such as echo similar to a string. Note the following points:

$ _ SESSION [test] = $ xml-> title; // save a SimpleXMLElement variable to the SESSION.

$ _ SESSION [test] = (string) $ xml-> title; // string

$ _ SESSION [test] = strval ($ xml-> title); // This is also true.