Symfony output image “”“Cannot modify header information - headers already sent by…”“” [duplicate]

问题

in /lib/Helper.class.php:

class Helper
{
  //... some functions
  static public function createImage( $src_image, $params)
  {
    $vars=array();
    foreach(array('angle'=>0,'font'=>'dejavu','font_size'=>20,'line_spacing'=>1.5,'preset'=>'BRCA','color'=>array(0,0,0),'text'=>'default text') as $key=>$value):

      $vars[$key]= array_key_exists($key, $params)?$params[$key]:sfConfig::get('app_default_poster_'.$key, $value);
    endforeach;

    extract($vars);
    $interval= $font_size*$line_spacing;
    $x=0;
    $y=0;
    $img_color = imagecolorallocate($src_image, $color[0], $color[1], $color[2]);
    $lines=explode("\n", $text);
    putenv('GDFONTPATH='.join(':',sfConfig::get('app_font_path')));
    $fontname=$font.'.ttf';
    foreach($lines as $i=>$line):

      imagettftext($src_image, $font_size, $angle, $x, $y+($i+1)*$interval, $img_color, $fontname, $line);

    endforeach;
    return $src_image;

  } 

  static public function createPoster( $params)
  {   
    $im= imagecreatefromjpeg(sfConfig::get('sf_web_dir').'/images/'.$params['preset'].'.jpg');
    return self::createImage($im, $params);
  }
  static public function createSidetape( $params)
  {

    $im= imagecreatetruecolor(sfConfig::get('app_sidetape_width'),sfConfig::get('app_sidetape_height'));
    $bg= imagecolorallocate($im, 255, 255, 255);
    imagefill($im, 0,0,$bg);
    return self::createImage($im , $params);
  } 


}

in my actions.class.php (of some module)

  public function executePreview(sfWebRequest $request)
  {
    $this->getResponse()->setHttpHeader('Content-type', 'image/jpeg');
    $this->setLayout(false);
    $img2=Helper::createPoster($request->getGetParameters());
    imagejpeg($img2, NULL, 10); 
    return sfView::NONE;

  }

now when I open /module/preview?text=Some+Text&preset=notice, I don't see correct image but its binary data along with a warning:

Warning: Cannot modify header information - headers already sent by (output started at /var/www/weblog/apps/backend/modules/poster/actions/actions.class.php:253) in /var/www/symfony/lib/response/sfWebResponse.class.php on line 336 Warning: Cannot modify header information - headers already sent by (output started at /var/www/weblog/apps/backend/modules/poster/actions/actions.class.php:253) in /var/www/symfony/lib/response/sfWebResponse.class.php on line 357

On the other hand, if I change $img2=Helper::createPoster($request->getGetParameters()); to $img2=Helper::createSidetape($request->getGetParameters()); in executePreview, I see an image. Why?

What's the problem in this?

回答1:

I modified executePreview to the following:

  public function executePreview(sfWebRequest $request)
  {
    $this->getResponse()->setHttpHeader('Content-type', 'image/jpeg');
    $this->setLayout(false);
    $img2=Helper::createPoster($request->getGetParameters());
    $this->getResponse()->sendHttpHeaders();
    imagejpeg($img2, NULL, 10); 
    return sfView::NONE;

  }

The problem was occuring because Symfony first sends Http headers and then the Content. both these calls are made in the view layer of the MVC. Now my action was calling imagejpeg hence sending output to the browser even before sendHttpHeaders was called by the framework. So I forced it to send Http header before actually sending image as output.

回答2:

this usually happens when php outputs error / warning messages before code like

 $this->getResponse()->setHttpHeader('Content-type', 'image/jpeg');

gets executed.

来源：https://stackoverflow.com/questions/8669589/symfony-output-image-cannot-modify-header-information-headers-already-sent

标签

php

symfony1

http-headers