Opcodes
PHP Manual

ASSIGN_OBJ

PHP code

<?php
/*
 * 
 * opcode number: 136
 */
$obj->$otherobj;
?>

PHP opcodes

Function name: (null)

Compiled variables: !0=$obj, !1=$otherobj

line#op fetchextreturn operands
60 ZEND_ASSIGN_OBJ     !0,'a'
 1 ZEND_OP_DATA     !1
72 RETURN     1

Opcodes
PHP Manual