Custom PHP settings that are applied to all plan subscriptions are defined by the php-settings node. This node is specified by complex type phpSettings (domain_template.xsd). This type is structured as follows:

php.ini configuration file. Say, memory_limit, safe_mode, and so on.php.ini configuration file. Say, for memory_limit it can be 128M or on for the safe_mode parameter. If you want to set the default value to a PHP parameter, send the request with the blank value node.
The following sample packet creates a service plan and sets the memory_limit and safe_mode settings:
<packet version="1.6.3.4">
<service-plan>
<add>
<name>base_plan</name>
<php-settings>
<setting>
<name>memory_limit</name>
<value>128M</value>
</setting>
<setting>
<name>safe_mode</name>
<value>on</value>
</setting>
</php-settings>
</add>
</service-plan>
</packet>