升级PHP到7.4版本：
转载于：https://www.cnblogs.com/vcdx/p/16262161.html
yum -y install epel-release yum-utils
yum install -y http://rpms.remirepo.net/enterprise/remi-release-7.rpm
yum-config-manager --disable remi-php54 #禁用php54
yum-config-manager --enable remi-php73 #启用php74
rpm -Uvh http://mirror.centos.org/centos/7/os/x86_64/Packages/graphite2-1.3.10-1.el7_3.x86_64.rpm
rpm -Uvh http://mirror.centos.org/centos/7/os/x86_64/Packages/harfbuzz-1.7.5-2.el7.x86_64.rpm
rpm -Uvh http://mirror.centos.org/centos/7/os/x86_64/Packages/fribidi-1.0.2-1.el7_7.1.x86_64.rpm
rpm -Uvh https://download-ib01.fedoraproject.org/pub/epel/7/x86_64/Packages/l/libraqm-0.7.0-4.el7.x86_64.rpm
systemctl stop httpd
yum update php*
systemctl start httpd
http://zabbixIP地址/zabbix/setup.php #必要条件检测，看检测是否都ok
不ok的，根据提示修改/etc/php.ini文件，重启httpd即可
升级PHP的作用：
安全性 速度 性能 产生巨大影响
大大减少内存使用量 从而确保更少的服务器每秒处理相同数量的请求