导入phing任务文件时出错，但文件存在

2.4.12 build。我将phing文件放在/opt/phing中，并添加.bashrc.

export PHP_COMMAND=/usr/bin/php 
export PHING_HOME=/opt/phing 
export PHP_CLASSPATH=${PHING_HOME}/classes 
export PATH=${PATH}:${PHING_HOME}/bin

我能够运行基本的phing脚本，但当我使用svexportdifftask时，它会抛出错误。

[PHP Error] include_once(phing/tasks/ext/svn/SvnExportDiffTask.php):
            failed to open stream: No such file or directory
            [line 1057 of /opt/phing/classes/phing/Phing.php]
[PHP Error] include_once(): Failed opening 'phing/tasks/ext/svn/SvnExportDiffTask.php'
            for inclusion (include_path='/opt/phing/classes:.:/home/prateek/work/bitnami/php/lib/php') 
            [line 1057 of /opt/phing/classes/phing/Phing.php]
  [foreach] Error importing phing/tasks/ext/svn/SvnExportDiffTask.php
Execution of target "getcode" failed for the following reason:
/home/prateek/work/build/build.xml:31:35:
Execution of the target buildfile failed. Aborting.
BUILD FAILED
/home/prateek/work/build/build.xml:31:35:
Execution of the target buildfile failed. Aborting.

有谁能帮我一下吗