The "pdo_mysql" extension is NOT loaded in your `php.ini`!
Make sure to load it before continuing!

yum install php-devel php-pear mysql-devel httpd-devel
pecl install pdo
PHP_PDO_SHARED=1 pecl install pdo_mysql

extension=pdo.so
extension=pdo_mysql.so

creating libtool
appending configuration tag "CXX" to libtool
configure: creating ./config.status
config.status: creating config.h
running: make
/bin/sh /root/tmp/pear/pear-build-rootLwk2BH/PDO_MYSQL-1.0.2/libtool --mode=compile cc -I -I/usr/include/mysql -g -fPIC -g -static-libgcc -fno-omit-frame-pointer -fno-strict-aliasing -DMY_PTHREAD_FASTMUTEX=1 -I. -I/root/tmp/pear/PDO_MYSQL -DPHP_ATOM_INC -I/root/tmp/pear/pear-build-rootLwk2BH/PDO_MYSQL-1.0.2/include -I/root/tmp/pear/pear-build-rootLwk2BH/PDO_MYSQL-1.0.2/main -I/root/tmp/pear/PDO_MYSQL -I/usr/local/include/php -I/usr/local/include/php/main -I/usr/local/include/php/TSRM -I/usr/local/include/php/Zend -I/usr/local/include/php/ext -I/usr/local/include/php/ext/date/lib  -DHAVE_CONFIG_H  -g -O2   -c /root/tmp/pear/PDO_MYSQL/pdo_mysql.c -o pdo_mysql.lo
mkdir .libs
 cc -I -I/usr/include/mysql -g -fPIC -g -static-libgcc -fno-omit-frame-pointer -fno-strict-aliasing -DMY_PTHREAD_FASTMUTEX=1 -I. -I/root/tmp/pear/PDO_MYSQL -DPHP_ATOM_INC -I/root/tmp/pear/pear-build-rootLwk2BH/PDO_MYSQL-1.0.2/include -I/root/tmp/pear/pear-build-rootLwk2BH/PDO_MYSQL-1.0.2/main -I/root/tmp/pear/PDO_MYSQL -I/usr/local/include/php -I/usr/local/include/php/main -I/usr/local/include/php/TSRM -I/usr/local/include/php/Zend -I/usr/local/include/php/ext -I/usr/local/include/php/ext/date/lib -DHAVE_CONFIG_H -g -O2 -c /root/tmp/pear/PDO_MYSQL/pdo_mysql.c  -fPIC -DPIC -o .libs/pdo_mysql.o
In file included from /root/tmp/pear/PDO_MYSQL/pdo_mysql.c:31:
/root/tmp/pear/PDO_MYSQL/php_pdo_mysql_int.h:25:19: error: mysql.h: No such file or directory
In file included from /root/tmp/pear/PDO_MYSQL/pdo_mysql.c:31:
/root/tmp/pear/PDO_MYSQL/php_pdo_mysql_int.h:36: error: expected specifier-qualifier-list before ‘MYSQL’
/root/tmp/pear/PDO_MYSQL/php_pdo_mysql_int.h:48: error: expected specifier-qualifier-list before ‘MYSQL_FIELD’
/root/tmp/pear/PDO_MYSQL/php_pdo_mysql_int.h:53: error: expected specifier-qualifier-list before ‘MYSQL_RES’
make: *** [pdo_mysql.lo] Error 1
ERROR: `make' failed