Use SimplePie to write twitter rss search results to a file.

recordTweets.php

<?php
	include( 'simplepie.php' );

	$sourceURL = 'feed://search.twitter.com/search.atom?q=+%22i+am+here+now%22&lang=all&rpp=100';

	$feed = new SimplePie();
	$feed->set_feed_url($sourceURL);
	$feed->set_timeout(10);
	$feed->enable_cache(true);
	$feed->init();
	$results = $feed->get_items( 0, 50 );
	
	// for debugging:
	// echo "<h1>Feed: $feed</h1>";
	// echo "<h1>results: ". count($results) ."</h1>";
	// echo "<h1>Now writing background:</h1>";
	$file = fopen("tweets/aggregate.txt", 'a+');
	if($file)
	{
		$filecontents = file_get_contents("tweets/aggregate.txt");
		$newstuff = "";
		$count = 0;
		foreach( $results as $tweet ){
			$content = str_ireplace( "I am here now", "<em>I am here now</em>", $tweet->get_title() );
			if( substr_count( $filecontents, $content ) == 0 )
			{
				$newstuff .= ($content."\n");
				$count++;
			}
		}
		fwrite($file, $newstuff);
		fclose($file);
		
		echo "<div>Added $count lines.</div>\n";
	}
	
?>