cakehp-tcpd错误:一些数据已经输出到浏览器，可以'；t在远程服务器上发送PDF文件

当尝试从远程服务器查看list_of_holidays.pdf时，我收到以下警告：

 Warning (2): Cannot modify header information - headers already sent by (output started    
 at /home/aquinto1/app/views/helpers/flash.php:155) [APP/vendors/tcpdf/tcpdf.php, line 8541]
 TCPDF ERROR: Some data has already been output to browser, can't send PDF file

第155行是flash.php中的最后一行，即php（？>）的结束标记。在此之前，它是嵌入SWF的代码。我看不出有什么不妥。

但是，它在本地服务器上显示良好。

我已经检查了空白，但错误仍然存在。

在输出之前，我已经在使用obclean了。

有人能告诉我我做错了什么吗。仅供参考，我正在将cakepp与tcpdf结合使用。

以下是flash.php

class FlashHelper extends AppHelper {     
var $helpers = array('Javascript'); 
/** 
 * Used for remembering options from init() to each renderSwf 
 * 
 * @var array 
 */ 
var $options = array( 
    'width' => 100, 
    'height' => 100 
); 
/** 
 * Used by renderSwf to set a flash version requirement 
 * 
 * @var string 
 */ 
var $defaultVersionRequirement = '9.0.0'; 
/** 
 * Used by renderSwf to only call init if it hasnt been done, either 
 * manually or automatically by a former renderSwf() 
 * 
 * @var boolean 
 */ 
var $initialized = false; 
/** 
 * Optional initializing for setting default parameters and also includes the 
 * swf library. Should be called once, but if using several groups of flashes, 
 * MAY be called several times, once before each group. 
 * 
 * @example echo $flash->init(); 
 * @example $flash->init(array('width'=>200,'height'=>100); 
 * @return mixed String if it was not able to add the script to the view, true if it was 
 */ 
function init($options = array()) { 
    if (!empty($options)) { 
        $this->options = am($this->options, $options); 
    } 
    $this->initialized = true; 
    $view =& ClassRegistry::getObject('view');  
    if (is_object($view)) {  
        $view->addScript($this->Javascript->link('swfobject'));  
        return true; 
    } else { 
        return $this->Javascript->link('swfobject'); 
    } 
} 
/** 
 * Wrapper for the SwfObject::embedSWF method in the vendor. This method will write a javascript code 
 * block that calls that javascript method. If given a dom id as fourth parameter the flash will  
 * replace that dom object. If false is given, a div will be placed at the point in the  
 * page that this method is echo'ed. The last parameter is mainly used for sending in extra settings to 
 * the embedding code, like parameters and attributes. It may also send in flashvars to the flash.  
 *  
 * For doucumentation on what options can be sent, look here: 
 * http://code.google.com/p/swfobject/wiki/documentation 
 * 
 * @example echo $flash->renderSwf('counter.swf'); // size set with init(); 
 * @example echo $flash->renderSwf('flash/ad.swf',100,20); 
 * @example echo $flash->renderSwf('swf/banner.swf',800,200,'banner_ad',array('params'=>array('wmode'=>'opaque'))); 
 * @param string $swfFile Filename (with paths relative to webroot) 
 * @param int $width if null, will use width set by FlashHelper::init() 
 * @param int $height if null, will use height set by FlashHelper::init() 
 * @param mixed $divDomId false or string : dom id 
 * @param array $options array('flashvars'=>array(),'params'=>array('wmode'=>'opaque'),'attributes'=>array()); 
 *         See SwfObject documentation for valid options 
 * @return string 
 */ 
function renderSwf($swfFile, $width = null, $height = null, $divDomId = false, $options = array()) { 
    $options = am ($this->options, $options);         
    if (is_null($width)) { 
        $width = $options['width']; 
    } 
    if (is_null($height)) { 
        $height = $options['height']; 
    } 
    $ret = ''; 
    if (!$this->initialized) { 
        $init = $this->init($options); 
        if (is_string($init)) { 
            $ret = $init; 
        } 
        $this->initialized = TRUE; 
    }         
    $flashvars = '{}'; 
    $params =  '{wmode : "opaque"}'; 
    $attributes = '{}'; 
    if (isset($options['flashvars'])) { 
        $flashvars = $this->Javascript->object($options['flashvars']); 
    } 
    if (isset($options['params'])) { 
        $params = $this->Javascript->object($options['params']); 
    } 
    if (isset($options['attributes'])) { 
        $attributes = $this->Javascript->object($options['attributes']); 
    } 
    if ($divDomId === false) { 
        $divDomId = uniqid('c_'); 
        $ret .= '<div id="'.$divDomId.'"></div>'; 
    } 
    if (isset($options['version'])) { 
        $version = $options['version']; 
    } else { 
        $version = $this->defaultVersionRequirement;             
    } 
    if (isset($options['install'])) { 
        $install = $options['install']; 
    } else { 
        $install =  '';             
    } 
    $swfLocation = $this->webroot.$swfFile; 
    $ret .= $this->Javascript->codeBlock( 
        'swfobject.embedSWF
("'.$swfLocation.'", "'.$divDomId.'", "'.$width.'", "'.$height.'", "'.$version.'",
            "'.$install.'", '.$flashvars.', '.$params.', '.$attributes.');'); 
        return $ret; 
    } 
 }
?>