如何从php文件的开头删除空格？

Have a PHP file which is making RSS feeds it is giving error because of the space appending before the output XML file. I have checked the code and the variable containing the variable $s which is making XML file does not have any white space before it.

<?php

  header("Content-Type: text/xml; encoding=UTF-8");
  $s = "<?xml version='1.0' encoding='UTF-8'?><rss version='2.0'><channel>"; 
 echo ltrim($s);

 foreach($this->results as $row)
  {
     $title=$row->name;
     $description=$row->description;  
     echo "<item><title>$title</title><link>$link</link><description>$description</description></item>"; 
  } 
  echo "</channel></rss>"; 

?>

Make sure no white space before <?php

<?php
header("Content-Type: text/xml; encoding=UTF-8");
$s = "<?xml version='1.0' encoding='UTF-8'?><rss version='2.0'><channel>"; 
echo ltrim($s);

foreach($this->results as $row)
{
$title=$row->name;
$description=$row->description;  
echo "<item><title>$title</title><link>$link</link><description>$description</description></item>"; 
} 

echo "</channel></rss>"; 

?>