<?php

    //PHPExcelをインクルード
    require_once(dirname(__FILE__) . '/Classes/PHPExcel.php');
    require_once(dirname(__FILE__) . '/Classes/PHPExcel/IOFactory.php');


    $filepath = "./test.xls";    //読み込みExcelファイルパス

    //Excel読み込み
    $objReader = PHPExcel_IOFactory::createReader('Excel5');
    $book = $objReader->load($filepath);

    //シート数取得
    $sheetsCount = $book->getSheetCount();

    for($i = 0; $i < $sheetsCount; $i++){
        //シート取得
        $book->setActiveSheetIndex($i);
        $sheet = $book->getActiveSheet();

        //シート名取得
        $sheetName = $sheet->getTitle();

        //シート名表示
        print "index" . $i . "：" . $sheetName . "<br>";
    }

?>

$sheetsCount = $book->getSheetCount();

$book->setActiveSheetIndex($i);

$sheet = $book->getActiveSheet();

$sheetName = $sheet->getTitle();

$sheetName = $book->getActiveSheet()->getTitle();