php parse iostat data and outputs it as json

iostat.php

<?php
/* requires sysstat: apt install sysstat */

function parseIostatLine($line)
{
$re = '/(?\'device\'[a-z0-9]{3}) \s* (?\'tps\'[\d\.]*) \s* (?\'readS\'[\d\.]*)\s*(?\'writeS\'[\d\.]*)\s*(?\'read\'[\d\.]*)\s*(?\'write\'[\d\.]*)/m';
preg_match_all($re, $line, $matches, PREG_SET_ORDER, 0);
if($matches[0]['read']==''&&$matches[0]['write']==''){return false;}
return array(
	"device"=>$matches[0]['device'],
	"write_per_second"=>$matches[0]['writeS'],
	"read_per_second"=>$matches[0]['readS'],
	"write"=>$matches[0]['write'],
	"read"=>$matches[0]['read'],
	"tps"=>$matches[0]['tps'] // transactions per second
);
}

$cmd = '/usr/bin/iostat -d -m';
exec($cmd,$lines,$ecode);

foreach ($lines as $line) {
	$io_res = parseIostatLine($line);
	$device=$io_res['device'];
	if($device=='') {continue;}
	$output[$device] = $io_res;
}

// json output
header("Content-Type: application/json; charset=utf-8");
echo json_encode($output);
?>