PHP: Bulk domain availability check!

<?php
set_time_limit(0);
ob_start();
/* 	--------	Bulk domain availablity check script (Revision 4) ------------		
[																					
[ 	Created by "Matthew." (#45276) @ http://namepros.com / http://toomanylines.com		
[	Feel free to modify/use however you wish,										
[	but keep credit comments in upon distribution.								
*/

include 'inc/dnservers.php';

function save_file($status) 
{
	global $filename, $domain, $extension;
	
	$domain = trim($domain);
	
	$file_handle = fopen($filename . "_$status.txt", 'a+') or trigger_error('Cannot open or create file (chmod?)', E_USER_WARNING);
	
	if($status == 'invalid' && $extension == 'org') { $status .= ' (.org WHOIS prevents request)'; }
				
	if(!fwrite($file_handle, $domain . " is $status\n"))
	{
		trigger_error('Results for ' . $domain . ' could not be written.', E_USER_WARNING);
	}
	
	fclose($file_handle);	
}

function return_status($domain, $status)
{	
	global $extension, $filename;

	
	$file = $filename;
	$domain = trim($domain);
	
	if(isset($_POST['save']))
	{
			save_file( $status );
	}
	else
	{	
		$color = ($status == 'available') ? 'green' : 'red';
		if($status == 'invalid' && $extension == 'org') { $status .= ' (.org WHOIS prevents request)'; }	
			
		echo "<div style=\"color: $color\">$domain is $status!</div>";
	}
}	
	
if(isset($_POST['submit']))
{
	$filename = 'saves/' . mt_rand(5, 9999999999);
		
	if(strlen($_POST['domains']) > 0)
	{

		$domains = explode("\n", $_POST['domains']);
		
		echo '<h1>Checking ' . count($domains) . ' domains</h1><br />';
		echo (isset($_POST['save'])) ? 'Preparing results, please wait...<br /><br />' : null;
		
		foreach($domains as $domain)
		{
			unset($buffer); // clean buffer - prevents problems
					
			// (replaced str_replace)	
			preg_match('@^(http://www\.|http://|www\.)?([^/]+)@i', $domain, $matches);
			$domain = $matches[2];
			
			$tld = explode('.', $domain, 2);
			$extension = strtolower(trim($tld[1]));
			
			if(strlen($domain) > 0 && array_key_exists('.' . $extension, $ext))
			{
				$server = $ext['.' .$extension][0];
				
				$sock = fsockopen($server, 43) or die('Error Connecting To Server:' . $server);
				fputs($sock, "$domain\r\n");
				
				while( !feof($sock) )
				{
				  	$buffer .= fgets($sock,128);
				}
			
				fclose($sock);
				if($extension == 'org') echo nl2br($buffer);
				
				if(eregi($ext['.' . $extension][1], $buffer)) { return_status($domain, 'available'); }
				
				else { return_status($domain, 'taken'); }
			}
			else
			{
				if(strlen($domain) > 0)	 { return_status($domain, 'invalid'); }
			}
		
			ob_flush(); // output before checking next domain
			flush();
			sleep(0.1);
		}
		
		if(isset($_POST['save']) && count($domains) > 0)
		{
			echo 'Check completed, your results can be found below:';
		
			if(file_exists($filename . '_available.txt'))
			{
				echo '<br /><a href="' . $filename . '_available.txt">Available domains</a>';
			}
			
			if(file_exists($filename . '_taken.txt'))
			{
				echo '<br /><a href="' . $filename . '_taken.txt">Taken domains</a>';
			}
			else
			{
				echo '<br />0 taken domains found';
			}
			
			if(file_exists($filename . '_invalid.txt'))
			{
				echo '<br /><a href="' . $filename . '_invalid.txt">Invalid domains (could not be checked)</a>';
			}
		}	
	}
	else
	{
		echo 'You need to enter one or more domains!';
	}
} 
else
{
	?>
<div style="text-align: center">
	<form action="index.php" method="post">
		<textarea name="domains" cols="100" rows="20"></textarea>
		<br /><input type="checkbox" name="save" value="save" /> Save results as text file?<br />
		<br /><input type="submit" name="submit" value="Check Availability" style="font-size: 30pt;" />
		
	</form>
</div>
	<?php
}
?>