Check if a Header Exists
You can check if a named header is present in a HeaderSet by calling its has() method.
To check if a header exists:
- Get the HeaderSet from the entity by via its getHeaders() method.
- Call the HeaderSet's has() method specifying the header you're looking for.
If the header exists, true will be returned or false if not.
Note:
It's valid for some headers to appear more than once in a message (e.g. the Received header).
For this reason has() accepts an optional numerical index, starting from zero
to specify which header you want to check more specifically.
$headers = $message->getHeaders();
//Check if the To: header exists
if ($headers->has('To')) {
echo 'To: exists';
}
//Check if an X-Foo header exists twice (i.e. check for the 2nd one)
if ($headers->has('X-Foo', 1)) {
echo 'Second X-Foo header exists';
}