loading PHP class body from external file

I want to include an external file as a class body, something like this:

//$key is alphanumeric
$className='_Module_'.$key;
if(!class_exists($className))
{
    eval(' class '.$className.' extends ModuleContext');
    {
        ...include the file here...
    }
}
eval('$instance=new '.$className.'();');

This does what I want:

//$key is alphanumeric
$className='_Module_'.$key;
if(!class_exists($className))
{
    //There's got to be a better way to do this
    $contents=rtrim(ltrim(trim(file_get_contents($fileName.'.php',true)),'<?php'),'?>');
    //All on one line to preserve line numbering for errors
    eval(' class '.$className.' extends ModuleContext{ '.$contents.' }');
}
eval('$instance=new '.$className.'();');

I don't like using eval to include the whole file because it generates confusing error messages:

PHP Fatal error:  Call to undefined function doFoo() in test/test.php(57) : eval()'d code on line 7

and I've read in 开发者_运维知识库other posts that eval()'d code doesn't take advantage of php accelerators. Also, it requres some trimming to remove the '<?php' and '?>' tags, since they don't work so well inside a class definition.

The included file needs to be 'user friendly' to someone who is familiar with PHP, but not object oriented programming - it will have a few pre-defined functions to be filled in by the module implementer.

Is there a way to do this that doesn't use eval for the include?

If I understand you correctly, ideally you would extend your class rather than trying to evaluate ad-hoc a body for your class:

class ClassA {
  public function greet( $msg ) {
    echo $msg;
  }
}

class ClassB extends ClassA {
  public function wave( $times ) {
    echo sprintf("Waves %s times!", $times);
  }
}

$instance = new ClassB();
$instance->greet("Hello World");
$instance->wave("five");

Note here how I'm able to build off of my class, adding new functionality and properties to the 'body' of it.

May by problem in non using short opening tag?