Aggregate array values into ranges

    // Output:
    // Array (
    //     [0] => Array ( [0] => 1, [1] => 2, [2] => 3, [3] => 4, [4] => 5, [5] => 6 )
    //     [1] => Array ( [0] => 10, [1] => 11, [2] => 12, [3] => 13 )
    //     [2] => Array ( [0] => 20 )
    //     [3] => Array ( [0] => 24 )
    // )
    static function GetRanges1( $aNumbers ) {
        $aNumbers = array_unique( $aNumbers );
        sort( $aNumbers );
        $aGroups = array();
        for( $i = 0; $i < count( $aNumbers ); $i++ ) {
          if( $i > 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
            array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
          else
            array_push( $aGroups, array( $aNumbers[$i] )); 
        }
        return $aGroups;
    }

    // Output: Array ( [0] => 1-6, [1] => 10-13, [2] => 20, [3] => 24 )
    static function GetRanges2( $aNumbers ) {
        $aNumbers = array_unique( $aNumbers );
        sort( $aNumbers );
        $aGroups = array();
        for( $i = 0; $i < count( $aNumbers ); $i++ ) {
          if( $i > 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
            array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
          else
            array_push( $aGroups, array( $aNumbers[$i] )); 
        }
        $aRanges = array();
        foreach( $aGroups as $aGroup ) {
          if( count( $aGroup ) == 1 )
            $aRanges[] = $aGroup[0];
          else
            $aRanges[] = $aGroup[0] . '-' . $aGroup[count($aGroup)-1];
        }
        return $aRanges;
    }

    // Output: 1~6,10~13,20,24
    static function GetRanges3( $aNumbers, $headChar='' ) {
        $aNumbers = array_unique( $aNumbers );
        sort( $aNumbers );
        $aGroups = array();
        for( $i = 0; $i < count( $aNumbers ); $i++ ) {
          if( $i > 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
            array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
          else
            array_push( $aGroups, array( $aNumbers[$i] )); 
        }
        $aRanges = array();
        foreach( $aGroups as $aGroup ) {
          if( count( $aGroup ) == 1 )
            $aRanges[] = $headChar.$aGroup[0];
          else
            $aRanges[] = $headChar.$aGroup[0] . '~' . $headChar.$aGroup[count($aGroup)-1];
        }
        return implode( ',', $aRanges );
    }