测试phpinfo没问题,wordpress正常，但切换到gitblog就报500

[cnrting]

centos7 PHP 5.4.16 (cli)
nginx的配置：
server {
listen 443;
listen [::]:443;
server_name xxx.com;
root /var/www/gitblogdoc;
index index.html index.htm index.php;
ssl_certificate "";
ssl_certificate_key "";
ssl_session_cache shared:SSL:1m;
ssl_session_timeout 10m;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE:ECDH:AES:HIGH:!NULL:!aNULL:!MD5:!ADH:!RC4;
ssl_prefer_server_ciphers on;

    location ~ \.(jpg|png|gif|js|css|swf|flv|ico)$ {
		expires 12h;
    }

    location / {
		if (!-e $request_filename) {
			rewrite ^(.*)$ /index.php?$1 last ;
			break;
		}
    }

    location ~* ^/(doc|logs|app|sys)/ {
        return 403;
    }

    location ~ \.php$ {
		try_files $uri =404;
		#fastcgi_pass unix:/var/run/php-fpm/php-fpm.sock;
		fastcgi_pass 127.0.0.1:9000;
		fastcgi_index index.php;
		fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
		include fastcgi_params;
	}
}

nginx 的错误日志：
[error] 32528#32528: 12256 FastCGI sent in stderr: "PHP message: PHP Fatal error: Call to undefined function mb_regex_encoding() in /var/www/gitblogdoc/app/libraries/Markdown.php on line 461" while reading response header from upstream, client: 113.110..*, server: xx.com, request: "GET / HTTP/2.0", upstream: "fastcgi://127.0.0.1:9000"