Topic on Project:Support desk

I am using a SMW extension , the code is as follows

<?php
	ini_set('display_errors', 'on');
	error_reporting(E_ALL);
	
	$wgExtensionCredits['other'][] = array(
		'name' => 'DoExample',
		'version' => '0.0.1',
		'author' => 'anirudhkv',
		'url' => '',
		'description' => 'To test an example SMW',
	);
	
	$wgHooks['ParserFirstCallInit'][] = array( 'Docall');
	$wgExtensionMessagesFiles['DoExample'] = __DIR__ . '/Doexample.i18n.php';
	
	
	function Docall(&$parser)
	{
		$parser->setFunctionHook( 'Doaction', 'callpage' );
		return true;
	}
	
	function callpage($output) {
		
		
		$params = array ("[[Category:Platform features]]", "?Buisness requirement=", "?Design=");
		$result1 = SMWQueryProcessor::getResultFromFunctionParams( $params, SMW_OUTPUT_WIKI );
	}

I am getting the following warning 4 times Cannot modify header information - headers already sent by (output started at /serverlocation/filename.php:1) in /serverlocation/includes/WebResponse.php on line 38 can some one help me out? what is the reason behind this

Look at /serverlocation/filename.php, Be sure you do not have anything (even whitespace) before the <?php tag

Yea got it :) thank you :)