动画GIF不会加载到<img src“”/>中

I'm creating an exit page for processing payments through Paypal. Now the problem is that I want display an animated GIF which doesn't load inside . I only get the static image. I've tried to add a preloading function onLoad() but nothing...

I would keep this structure

  • html
  • logo
  • message
  • animated gif (loader)

This is my code

  <?php
  echo "<html>
";
  echo "<head><title>Processing Payment...</title></head>
";
  echo "<body style=\"background:#313B54\" onLoad=\" document.form.submit();\">
";
  echo "<center style=\"height:100%\">
";
  echo "<img style=\"display:block; margin-top:35px\" src=\"".get_bloginfo('template_url')."/lib/gateways/ux/kleeia-logo.png\"/>
";
  echo "<h3 style=\"color:#fff; margin-top:35px\">Please wait, your payment is being processed.</h3>
";
  echo "<img src=\"".get_bloginfo('template_url')."/lib/gateways/ux/kleeia-loader.gif\"/>
";
  echo "</center>
";
  echo "<form method=\"post\" name=\"form\" action=\"".$this->paypal_url."\">
";

  foreach ($this->fields as $name => $value) {
     echo "<input type=\"hidden\" name=\"$name\" value=\"$value\">";
  }
  echo "</form>
";
  echo "</body></html>
"; ?>

Thanks in advance for your help.