Php scripts : problem with whitespace

Recently while working on some project I faced a strange problem. In one of our app we were trying to implement and call a service using hessian. But somehow we were getting malformed reply for all the requests. We checked all the scripts and there were no problems in any of them. Finally, after a lot of efforts we got the problem. The problem was very simple, in one of the scripts there were some blank lines before the php start tag (<?php)

Leaving whitespaces (spaces/line breaks etc) before or after php scripts can be problematic and can result in unexpected or undesirable behaviour. Since these whitespaces will be echoed to the browser along with the normal output, It can break any script attempting to send headers (e.g. initializing session, sending content type, etc.) and can distort the web page layout.

Here is a simple php script that will scan php files in a given directory (and its subdirectories) and will remove all the whitespaces.

<?php
$maindir = "/path_to_the_project_dir";

define("PRE", "/^[\n\r|\r\n|\n|\r|\s]+<\?php/");
define("POST", "/\?>[\n\r|\r\n|\n|\r|\s]+$/");

clearstatcache();

if(scan_dir( $maindir, "removeWSpace", true ) === false)
{
echo "'{$maindir}' is not a valid directory\n";
}

function scan_dir( $maindir, $callback, $recursive = true )
{
$dh = @opendir( $maindir );
if( $dh === false)
return false;

while( $file = readdir( $dh ))
{
if( "." == $file || ".." == $file )
{
continue;
}
call_user_func( $callback, "{$maindir}/{$file}" );
if( $recursive !== false && is_dir( "{$maindir}/{$file}" ))
{
scan_dir( "{$maindir}/{$file}", $callback, $recursive );
}
}
closedir( $dh );
return true;
}

function removeWSpace( $path )
{
if( !is_dir( $path ) && substr($path, -4) == ".php")
{
$fh = file_get_contents($path);
$fh = preg_replace(PRE, ' 0 || $c2 > 0)
{
if(file_put_contents($path, $fh))
echo $path . " -- modified \n";
}
}
}

?>