VLD是php的一个扩展，用于查看php的Opcode级的操作。

VLD包的下载网址：http://pecl.php.net/package/vld

用php的pecl安装方法：pecl install channel://pecl.php.net/vld-0.10.1

使用方法如：
1、用于测试的文件为testvld.php，内容如下
function _count($num){
   if($num==0){
        return 0;
   }else{
        return $num + _count($num-1);
   }
}
echo _count(10);
?>

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2、根据各自的环境来用php命令加-dvld.active=1来执行文件，如本人环境中执行命令：/usr/local/php-5.6.4/bin/php -c /usr/local/php-5.6.4/php.ini  -dvld.active=1 testvld.php 

3、通过vld对testvld.php执行结果如下：
Finding entry points
Branch analysis from position: 0
Jump found. Position 1 = -2
filename:       /home/file/testvld.php
function name:  (null)
number of ops:  5
compiled vars:  none
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   2     0  E >   NOP                                                      
   9     1        SEND_VAL                                                 10
         2        DO_FCALL                                      1  $0      '_count'
         3        ECHO                                                     $0
  11     4      > RETURN                                                   1

branch: #  0; line:     2-   11; sop:     0; eop:     4; out1:  -2
path #1: 0,
Function _count:
Finding entry points
Branch analysis from position: 0
Jump found. Position 1 = 3, Position 2 = 5
Branch analysis from position: 3
Jump found. Position 1 = -2
Branch analysis from position: 5
Jump found. Position 1 = -2
filename:       /home/file/testvld.php
function name:  _count
number of ops:  12
compiled vars:  !0 = $num
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   2     0  E >   RECV                                             !0      
   3     1        IS_EQUAL                                         ~0      !0, 0
         2      > JMPZ                                                     ~0, ->5
   4     3    > > RETURN                                                   0
   5     4*       JMP                                                      ->11
   6     5    >   INIT_FCALL_BY_NAME                                       '_count'
         6        SUB                                              ~1      !0, 1
         7        SEND_VAL                                                 ~1
         8        DO_FCALL_BY_NAME                              1  $2      
         9        ADD                                              ~3      !0, $2
        10      > RETURN                                                   ~3
   8    11*     > RETURN                                                   null

branch: #  0; line:     2-    3; sop:     0; eop:     2; out1:   3; out2:   5
branch: #  3; line:     4-    4; sop:     3; eop:     3; out1:  -2
branch: #  5; line:     6-    8; sop:     5; eop:    11
path #1: 0, 3,
path #2: 0, 5,
End of function _count

重点分析：
number of ops:  Opcode级的操作总个数
列表中的op:具体的操作名

网站题目：PHP用VLD查看php的Opcode级执行
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