<?php
   $len = 5;
   $output = array();
   for( $i = 1; $i < pow( 2, $len ); $i++ ) {
      $line = array();
      for( $j = 0; $j < $len; $j++ ) {
         if( ( 1 << $j ) & $i ) $line[] = $j + 1;
      }
      $output[count($line)][] = $line;
   }
   
   foreach( $output as $group ) {
      foreach( $group as $line ) {
         foreach( $line as $item ) echo "$item ";
         echo "\n";
      }
   }
?>