Basic question: What is the object reference problem?

Basic question: What is the object reference problem?

 My_val = 5; global $ global_obj; $ global_obj-> my_val = 10; echo $ p-> my_val; // output 5var_dump ($ p = $ global_obj ); // return false?>

Why is the result 5 instead of 10;
My understanding is: in PHP5, unless you explicitly want to clone an object with the clone keyword, the object will never be unconsciously copied.
Is that true?

Reply to discussion (solution)

Row 8th $ global_obj = & $ this,
18th rows
Creating default object from empty value (create default object from null value)
Warning, you have blocked the error information, so you cannot figure out why

When the value of row 8th is corrected to $ global_obj = $ this;
You can output 10.

Look at the http://php.net/manual/zh/language.oop5.references.php recommended