废话不多说，直接上问题：
PHP和openssl extension都是最新版本的，标准步骤安装时候出现如下问题：
php：php-5.6.27
openssl：openssl-1.1.0e
================================
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3536:31: error: dereferencing pointer to incomplete type
int len = BN_num_bytes(pkey->pkey._type->_name);
^
/usr/local/openssl/include/openssl/bn.h:142:40: note: in definition of macro ‘BN_num_bytes’
# define BN_num_bytes(a) ((BN_num_bits(a)+7)/8)
^
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3982:5: note: in expansion of macro ‘OPENSSL_PKEY_GET_BN’
OPENSSL_PKEY_GET_BN(dh, g);
^
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3538:18: error: dereferencing pointer to incomplete type
BN_bn2bin(pkey->pkey._type->_name, (unsigned char*)str);
^
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3982:5: note: in expansion of macro ‘OPENSSL_PKEY_GET_BN’
OPENSSL_PKEY_GET_BN(dh, g);
^
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3535:11: error: dereferencing pointer to incomplete type
if (pkey->pkey._type->_name != NULL) {
^
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3983:5: note: in expansion of macro ‘OPENSSL_PKEY_GET_BN’
OPENSSL_PKEY_GET_BN(dh, priv_key);
^
In file included from /usr/local/openssl/include/openssl/asn1.h:24:0,
from /usr/local/openssl/include/openssl/objects.h:916,
from /usr/local/openssl/include/openssl/evp.h:27,
from /root/software/php/php-5.6.27/ext/openssl/openssl.c:44:
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3536:31: error: dereferencing pointer to incomplete type
int len = BN_num_bytes(pkey->pkey._type->_name);
^
/usr/local/openssl/include/openssl/bn.h:142:40: note: in definition of macro ‘BN_num_bytes’
# define BN_num_bytes(a) ((BN_num_bits(a)+7)/8)
^
/root/software/php/php-5.6.27/ext/openssl/openssl.c:3983:5: note: in expansion of macro ‘OPENSSL_PKEY_GET_BN’
OPENSSL_PKEY_GET_BN(dh, priv_key);
^
/root/software/php
================================
在网上搜索了一圈，都没有答案。
于是打开代码看来一下，看来某些定义的头文件没有引用进来。
但如本人才疏学浅，对openssl没有整体的把握，所以就对比了之前的openssl版本，发现版本升级后，代码是有变化的。
具体细节大家可以自己去看。
解决办法就是：
把openssl的版本降级，我选择的是openssl-0.9.8v。
重新编译安装，就不会有编译错误了。