- array_map: documentation ( source)
- phpversion: documentation ( source)
- print_r: documentation ( source)
- array_keys: documentation ( source)
<?php
$headers = array(
'From' => 'webmaster@example.com',
'Reply-To' => 'webmaster@example.com',
'X-Mailer' => 'PHP/' . phpversion(),
);
print_r(array_join(array_map(
function ($v, $k) { return $k . ': ' . $v; },
$headers,
array_keys($headers)
), '\r\n'));