&lang['example'] in new php. need help

Hello all! My problem is:

I`ve a php, in which describes some functions only. For the example i`ll post a part of the code

PHP Code: [Select] [Expand] [Hide line numbers]

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echo '<br><br><select name="drop_3" id="drop_3">
	
      <option value=" " disabled="disabled" selected="selected">Choose Example</option>
	
      <option value="unknown">Unknown</option>
	
      <option value="Type Manually Airline Here">Unlisted - Type Manually</option>
	
      <option value=" " disabled="disabled">---------------------</option>';

Choose Example, Unlisted - Type Manually, Unknown can`t support $lang['choose_example']... Got me error, lang is unknown... How to do this. Help me please! Many thanks!