解决办法：
在php.ini中将max_input_vars调大改为5000就可以了
原因追查：
from的enctype="multipart/form-data"
php版本5.6.6
问题：部分POST数据接收不到
追源代码发现是php中max_input_vars配置造成的；
相关函数为rfc1867_post_handler，如果超过长度，则不会调用safe_php_register_variable来进行变量注册
相关堆栈如下
#0 rfc1867_post_handler (
content_type_dup=0x7ff85307a5f8 "multipart/form-data; boundary=", '-' <repeats 27 times>, "306141311912057",
arg=0x7ff85307ccc0) at /tmp/php-5.6.2/main/rfc1867.c:681
#1 0x00000000007a4bb0 in sapi_handle_post (arg=<value optimized out>) at /tmp/php-5.6.2/main/SAPI.c:185
#2 0x00000000007ab72f in php_default_treat_data (arg=0, str=0x0, destArray=0x7ff85307ccc0)
at /tmp/php-5.6.2/main/php_variables.c:399
#3 0x0000000000615c91 in mbstr_treat_data (arg=0, str=0x0, destArray=0x0) at /tmp/php-5.6.2/ext/mbstring/mb_gpc.c:69
#4 0x00000000007aa9fb in php_auto_globals_create_post (name=0x7ff852f474f0 "_POST", name_len=5)
at /tmp/php-5.6.2/main/php_variables.c:741
#5 0x00000000007d63bb in zend_auto_global_init (auto_global=0x196c950) at /tmp/php-5.6.2/Zend/zend_compile.c:6832
#6 0x0000000000808a43 in zend_hash_apply (ht=0x1955cb0, apply_func=0x7d63a0 <zend_auto_global_init>)
at /tmp/php-5.6.2/Zend/zend_hash.c:641
#7 0x00000000007aaa4e in php_hash_environment () at /tmp/php-5.6.2/main/php_variables.c:702
#8 0x000000000079bb25 in php_request_startup () at /tmp/php-5.6.2/main/main.c:1671
#9 0x00000000008a756d in main (argc=<value optimized out>, argv=<value optimized out>)
at /tmp/php-5.6.2/sapi/fpm/fpm/fpm_main.c:1887
其中rfc1867_post_handler为php_session_rfc1867_callback
完~
