Opcodes
PHP Manual

POST_DEC_OBJ

PHP code

<?php
/*
 * 
 * opcode number: 135
 */
$obj = new A();
$obj->num--;
?>

PHP opcodes

Function name: (null)

Compiled variables: !0=$obj

line#op fetchextreturn operands
60 ZEND_FETCH_CLASSВ  В :0 'A'
В 1 NEWВ  В $1 :0
В 2 DO_FCALL_BY_NAMEВ  0В  В 
В 3 ASSIGNВ  В В  !0,$1
74 ZEND_POST_DEC_OBJВ  В ~5 !0,'num'
В 5 FREEВ  В В  ~5
86 RETURNВ  В В  1

Opcodes
PHP Manual