Netbeans code completion api

Question

I am attempting to make a Netbeans 7.2 code completion module. I am trying to have this code completion to only show up for only PHP. I am also trying to have the code completion to only show up with specific methods/function ie x() and z().

I am new at this. I followed this tutorial http://platform.netbeans.org/tutorials/nbm-code-completion.html to get a brief understanding of the API.

How can I determine what method/function the code completion is being rendered on?

Let me know if you need additional information.

EDIT

I am trying to make it so the code completion is on the 1st parameter of function x() and z()

UPDATE

This is what I have thus far:

return new AsyncCompletionTask(new AsyncCompletionQuery() {
    protected void query(CompletionResultSet completionResultSet, Document document, int caretOffset) {

        String filter = null;
        int startOffset = caretOffset - 1;

        try {
            final StyledDocument bDoc = (StyledDocument) document;
            final int lineStartOffset = getRowFirstNonWhite(bDoc, caretOffset);
            final char[] line = bDoc.getText(lineStartOffset, caretOffset - lineStartOffset).toCharArray();
            final int whiteOffset = indexOfWhite(line);
            filter = new String(line, whiteOffset + 1, line.length - whiteOffset - 1);
            if (whiteOffset > 0) {
                startOffset = lineStartOffset + whiteOffset + 1;
            } else {
                startOffset = lineStartOffset;
            }
        } catch (BadLocationException ex) {
            Exceptions.printStackTrace(ex);
        }

        if(filter.startsWith("x('") || filter.startsWith("z('"))
        {
            // This is what I would assume is the first param.
            String result = filter.replaceFirst("x('|z('", "");
        }
    }
}, jtc);