在运行php -m时报错：

PHP Warning:  PHP Startup: Unable to load dynamic library 'mysqli.so' (tried: /usr/lib64/php/modules/mysqli.so (/usr/lib64/php/modules/mysqli.so: symbol mysql_change_user, version libmysqlclient_18 not defined in file libmysqlclient.so.18 with link time reference), /usr/lib64/php/modules/mysqli.so.so (/usr/lib64/php/modules/mysqli.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/pdo_mysql.so' (tried: /usr/lib64/php/modules/pdo_mysql.so (/usr/lib64/php/modules/pdo_mysql.so: symbol mysql_options, version libmysqlclient_18 not defined in file libmysqlclient.so.18 with link time reference), /usr/lib64/php/modules//usr/lib64/php/modules/pdo_mysql.so.so (/usr/lib64/php/modules//usr/lib64/php/modules/pdo_mysql.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
PHP Warning:  PHP Startup: Unable to load dynamic library 'mysqli.so' (tried: /usr/lib64/php/modules/mysqli.so (/usr/lib64/php/modules/mysqli.so: symbol mysql_change_user, version libmysqlclient_18 not defined in file libmysqlclient.so.18 with link time reference), /usr/lib64/php/modules/mysqli.so.so (/usr/lib64/php/modules/mysqli.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
PHP Warning:  PHP Startup: Unable to load dynamic library 'pdo_mysql.so' (tried: /usr/lib64/php/modules/pdo_mysql.so (/usr/lib64/php/modules/pdo_mysql.so: symbol mysql_options, version libmysqlclient_18 not defined in file libmysqlclient.so.18 with link time reference), /usr/lib64/php/modules/pdo_mysql.so.so (/usr/lib64/php/modules/pdo_mysql.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
看起来有一大堆东西。实际上这几个都有一个共同的一句话，那就是上面标红的那部分

其实这是因为libmysqlclient.so.18这个文件冲突了，我们可以看一下：

[root@VM_0_9_centos ~]# find / -name "libmysqlclient.so.18"
/home/mysql/lib/libmysqlclient.so.18
/usr/lib64/libmysqlclient.so.18

我们发现实际上已经存在两个这玩意，这肯定会冲突，而且php肯定是使用第二个，然而第二个并不行，我们需要的是mysql带的lib，因此，我们直接将第二个干掉，然后增加一个软链即可：

[root@VM_0_9_centos ~]# ln -s /home/mysql/lib/libmysqlclient.so.18 /usr/lib64/libmysqlclient.so.18
ln: failed to create symbolic link ‘/usr/lib64/libmysqlclient.so.18’: File exists
[root@VM_0_9_centos ~]# rm -rf /usr/lib64/libmysqlclient.so.18
[root@VM_0_9_centos ~]# ln -s /home/mysql/lib/libmysqlclient.so.18 /usr/lib64/libmysqlclient.so.18

然后再次运行php -m就不会出错了