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функция не описана

YoastSEO_Vendor\Psr\Http\Message

MessageInterface::getHeaders() public Yoast 1.0

Retrieves all message header values.

The keys represent the header name as it will be sent over the wire, and each value is an array of strings associated with the header.

// Represent the headers as a string
foreach ($message->getHeaders() as $name => $values) {
	echo $name . ": " . implode(", ", $values);
}
// Emit headers iteratively:
foreach ($message->getHeaders() as $name => $values) {
	foreach ($values as $value) {
		header(sprintf('%s: %s', $name, $value), false);
	}
}

While header names are not case-sensitive, getHeaders() will preserve the exact case in which headers were originally specified.

{} Это метод класса: MessageInterface{}

Хуков нет.

Возвращает

Строку[][]. Returns an associative array of the message's headers. Each

    key MUST be a header name, and each value MUST be an array of strings
	for that header.

Использование

$MessageInterface = new MessageInterface();
$MessageInterface->getHeaders();

Код MessageInterface::getHeaders() Yoast 15.3

<?php
public function getHeaders();