How to check in Phing if a file or directory exists?

To check dirs:

<exec command="if [ -d '/path/to/dir' ]; then echo 'true'; else echo 'false'; fi;" outputProperty="output.IS_DIRECTORY_EXISTS" />
<if>
    <equals arg1="${output.IS_DIRECTORY_EXISTS}" arg2="true" />
    <then>
        <!-- If dir exists -->
    </then>
    <else>
        <!-- If dir doesn't exist -->
    </else>
</if>

To check files:

<property name="output.IS_FILE_EXISTS" value="false" />
<exec command="if [ -f '/path/to/file' ]; then echo 'true'; else echo 'false'; fi;" outputProperty="output.IS_FILE_EXISTS" />
<if>
    <equals arg1="${output.IS_FILE_EXISTS}" arg2="true" />
    <then>
        <!-- If file exists -->
    </then>
    <else>
        <!-- If file doesn't exist -->
    </else>
</if>