In 0.9.7,
all MODx tags will accept modifiers and parse them as defined in the class modInputFilter. Each element will then have a chance to go through additional processing according to modOutputFilter, after normal processing completes. These filter classes can be set in global system configuration settings, and overridden by context-specific configuration settings, or even set programmatically for a specific element with MODx API code. Overriding the behavior will be as simple as extending one or both of the filter classes and implementing the methods you wish to alter.
Consider the following tag scenarios in 0.9.7:
[[Snippet? ¶m=`[[AnotherSnippet? ¶m=`[[*alias:ucase]]`]]` ¶m2=`[[~[[++site_start]]]]:xhtml`]]
[[[[+snippet_prefix]]Snippet? ¶m=`[[$ChunkThatHoldsParamValue:lcase]]`]]
I haven’t done any work with the conditional features of phX yet, but I will try and post some additional information on how/if the functionality of conditional modifiers will change with the new core.