set_include_path
    (PHP 4 >= 4.3.0, PHP 5)
set_include_path -- 
     Sets the include_path configuration option
    
Description
string 
set_include_path ( string new_include_path )
     Sets the include_path 
     configuration option for the duration of the script.  Returns the old 
     include_path on success or 
     FALSE on failure.
    
     
Example 1. set_include_path() example 
<?php // Works as of PHP 4.3.0 set_include_path('/inc');
  // Works in all PHP versions ini_set('include_path', '/inc'); ?>
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Example 2. Adding to the include path 
       Making use of the PATH_SEPARATOR
       constant, it is possible to extend the include path
       regardless of the operating system.
       
       In this example we add /usr/lib/pear
       to the end of the existing include_path.
       
<?php $path = '/usr/lib/pear'; set_include_path(get_include_path() . PATH_SEPARATOR . $path); ?>
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     See also ini_set(),
     get_include_path(),
     restore_include_path(), and
     include().