- substr: documentation ( source)
- strpos: documentation ( source)
- str_replace: documentation ( source)
<?php
$variable_name = 'field_bundle_settings_my_type__my_field__name';
$name = str_replace('field_bundle_settings_', '', $variable_name);
$entity_type = substr($name, 0, strpos($name, '__'));
$bundle = substr($name, strpos($name, '__') + 2);
print $entity_type . "\n";
print $bundle;