5005 /**

  5006  * Implementation of the "which" command in native PHP.

  5007  * @param string command

  5008  * @return string path to executable, or false on failure

  5009  */

  5010 

  5011 function which($executable)

  5012 {

  5013   $path = ( isset($_ENV['PATH']) ) ? $_ENV['PATH'] : ( isset($_SERVER['PATH']) ? $_SERVER['PATH'] : false );

  5014   if ( !$path )

  5015     // couldn't get OS's PATH

  5016     return false;

  5017     

  5018   $win32 = ( PHP_OS == 'WINNT' || PHP_OS == 'WIN32' );

  5019   $extensions = $win32 ? array('.exe', '.com', '.bat') : array('');

  5020   $separator = $win32 ? ';' : ':';

  5021   $paths = explode($separator, $path);

  5022   foreach ( $paths as $dir )

  5023   {

  5024     foreach ( $extensions as $ext )

  5025     {

  5026       $fullpath = "$dir/{$executable}{$ext}";

  5027       if ( file_exists($fullpath) && is_executable($fullpath) )

  5028       {

  5029         return $fullpath;

  5030       }

  5031     }

  5032   }

  5033   return false;

  5034 }

  5035