• see what is installed (assuming php-mcrypt & php-mhash are installed

yum list installed | grep php | cut -d' ' -f1
typical result:
php.x86_64
php-cli.x86_64
php-common.x86_64
php-devel.x86_64
php-gd.x86_64
php-imap.x86_64
php-ldap.x86_64
php-mbstring.x86_64
php-mcrypt.x86_64
php-mhash.x86_64
php-mysql.x86_64
php-odbc.x86_64
php-pdo.x86_64
php-pear.noarch
php-xml.x86_64
php-xmlrpc.x86_64

• removes the 16 packages above (make sure there is nothing above you want to keep)
  • Check that only the packages above are listed before you press yes

yum remove php php-*

In a Red Hat or CentOS server installation, XMLwriter may not be enabled by default. To enable it, follow these steps:

# If you are using the base 5.1.6 php, then
yum -y install php-xml

#if you are using php 5.2 (from the centos 5 testing repo)
yum -y --enablerepo=c5-testing install php-xml

#restart apache
service httpd restart

There are some problems with running Drupal on php 5.3. There are five kinds of solutions:

1. Downgrade to php 5.2.6 (not possible in many situations)
2. modify Drupal to change the error level reporting
3. find the latest patches to fix the problems
4. hack Drupal core or contrib yourself to fix the errors (Drupal 6 is already compliant, but not D5)
5. put a timezone in your php.ini to get rid of timezone errors

Drupal 6

2. Modify Drupal's error reporting --already done for Drupal 6

3. Find patches

This are probably not of general interest, just some example queries from a particular database that I wanted to save here as snippets.

--view all category titles from node: n & d, category node: c
$sql="SELECT n.nid, c.title AS cname, d.field_catcache_value AS cat FROM node AS n"
. " JOIN content_type_document AS d ON d.nid=n.nid AND d.vid=n.vid"
. " JOIN node AS c ON c.nid=d.field_category_nid"
. " WHERE n.type = 'document'";

--get the body of the category definition c from a given node n & d
SELECT n.nid, c.title, r.body AS cname FROM node AS n

Single node output: Sony use Drupal

Get many items using an object

pre{border:none;background-color:#f4f3d7;padding:1em;-moz-border-radius:10px}

<?php
exec("mysqldump -uDBUSER -pPASSWORD DBNAME > DBNAME.sql");
exec("tar -czvf BACKUP.tar.gz .");
print "Done";