Split ONIX files into smaller chunks

class.onixSplitter.php

<?php
class onixSplitter
{
	function split($file,$header,$footer,$split_at=2000)
	{
		$this->file = $file;
		$this->header = $header;
		$this->footer = $footer;
		$this->split_at = $split_at;
		$this->write_num = 1; // starting number for files written
		
		$this->read($this->file);
		
	}
	
	function explodeHeader()
	{
		$return = explode("\n",$this->header);
		foreach($return as $k => $v){
			$return[$k] = trim($v);
		}
		return $return;
	}
	
	
	function read()
	{
		$handle = fopen($this->file, "r");
		if ($handle)
		{
			$header_array = $this->explodeHeader();
		    $write = array();
			$count = 0;
			while (($line = fgets($handle)) !== false)
			{
				if(!in_array(trim($line),$header_array) AND $line != $this->footer)
				{
					$check = trim(strtolower($line));
					if($check == '<product>'){
						$write[$count] = '';
					}
					
					$write[$count] .= $line;

					
					if($check == '</product>'){
						++$count;
					}
					
					if($count == $this->split_at)
					{
						$this->writeSplit($write);

						unset($write);
						$count = 0;
					}
				}
			}
			
			// write remaining lines
			if(isset($write))
			{
				$this->writeSplit($write);
			}
			
		}
	}
	
	function writeSplit($data)
	{
		$p = pathinfo($this->file);
		$file = $p['dirname'].'/'.$p['filename'].'-'.$this->write_num.'.'.$p['extension'];
		
		$fp = fopen($file, 'w');
		fwrite($fp, $this->header.PHP_EOL);
		
		foreach($data as $k => $v){
			fwrite($fp, $data[$k].PHP_EOL);
		}
		fwrite($fp, $this->footer);
								
		fclose($fp);
		
		++$this->write_num;
	}
}

$header = '<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE ONIXmessage SYSTEM "http://www.editeur.org/onix/2.1/short/onix-international.dtd">
<ONIXmessage>
<header>
<m173>2013975</m173>
<m174>Random House, LLC</m174>
<m175>Content Management Group</m175>
<m283>RHContentManagementGroup@randomhouse.com</m283>
<m180>653</m180>
<m182>201402020831</m182>
<m183>FULLCAT; Full product extraction</m183>
</header>';
$footer = '</ONIXMessage>';

$split = new onixSplitter;
$split->split('/path/to/onix.xml',$header,$footer,200);