How to get the header information of http request in php

<?php
foreach (getallheaders() as $name => $value) {
echo "$name: $value\n";
}
?>

<?php
if (!function_exists(&#39;getallheaders&#39;))
{
function getallheaders()
{
foreach ($_SERVER as $name => $value)
{
if (substr($name, 0, 5) == &#39;HTTP_&#39;)
{
$headers[str_replace(&#39; &#39;, &#39;-&#39;, ucwords(strtolower(str_replace(&#39;_&#39;, &#39; &#39;, substr($name, 5)))))] = $value;
}
}
return $headers;
}
}
?>

<?php
print_r(getallheaders());

Array
(
[Accept] => */*
[Accept-Language] => zh-cn
[Accept-Encoding] => gzip, deflate
[User-Agent] => Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727)
[Host] => localhost
[Connection] => Keep-Alive
)