1.通过：phpinfo()去找 error_log 结果得到：
error_log no value
2.然后去编辑php.ini，修改三处地方

vi /etc/php.ini

error_log = /var/log/php_errors.log
display_errors = on
# 开发环境设置值: E_ALL
# 生产环境设置值: E_ALL & ~E_DEPRECATED & ~E_STRICT
error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT

赋权限

touch /var/log/php_errors.log
chmod +rw /var/log/php_errors.log

重启php-fpm

systemctl stop php-fpm
systemctl start php-fpm

参考：CentOS 7中设置PHP7的Log文件日志