PHP Float error

Hi all,
i build a php 5.6.30 for my router (AR71xx) , it works, but has some strange problems.
i also build for ralink mt7620 cpu,it has the same problem,but BCM5300 cpu works fine.
root@lede:~# ./php -v
PHP 5.6.30 (cli) (built: Feb 13 2017 13:04:47)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
but any function about float(round,floor,mod and forced type conversion ) will cause Segmentation fault , Bus error or stuck , even run php -i , will stop at _SERVER["REQUEST_TIME_FLOAT"] => , but the offical OPKG package works fine. I have no idea about this.
Here is my configure : Configure Command => './configure' '--host=mips-openwrt-linux-musl' '--prefix=/home/AR71xx/php_musl' '--disable-all' '--enable-posix' '--enable-pcntl' '--enable-json' '--enable-session' '--disable-phpdbg' '--disable-cgi' 'host_alias=mips-openwrt-linux-musl'
Sorry for my bad english.