Make sure you check for bzerror while looping through a bzfile. bzread will not detect a compression error and can continue forever even at the cost of 100% cpu.
$fh = bzopen('file.bz2','r');
while(!feof($fh)) {
$buffer = bzread($fh);
if($buffer === FALSE) die('Read problem');
if(bzerror($fh) !== 0) die('Compression Problem');
}
bzclose($fh);