WireHttp::setHeader() method   
Send an individual request header to send with GET/POST/etc. request
Usage
$http->setHeader(string $key, string $value);Arguments
| Name | Type(s) | Description | 
|---|---|---|
| $key | string | Header name | 
| $value | string | Header value to set (or specify null to remove header, 3.0.131 | 
Return value
$thisObject instance it was called from (method supports fluent interface).
API reference based on ProcessWire core version 3.0.252