diff --git a/composer.json b/composer.json
index 735fb8e403e..89e0409c946 100644
--- a/composer.json
+++ b/composer.json
@@ -36,6 +36,7 @@
 		"php": ">=7.2.22",
 		"psr/container": "1.0.0",
 		"psr/log": "1.1.3",
+		"ralouphie/getallheaders": "3.0.3",
 		"wikimedia/assert": "0.5.0",
 		"wikimedia/at-ease": "2.0.0",
 		"wikimedia/base-convert": "2.0.1",
diff --git a/includes/Rest/RequestFromGlobals.php b/includes/Rest/RequestFromGlobals.php
index e98db12c524..5d2f69484ec 100644
--- a/includes/Rest/RequestFromGlobals.php
+++ b/includes/Rest/RequestFromGlobals.php
@@ -54,22 +54,7 @@ class RequestFromGlobals extends RequestBase {
 	}
 
 	protected function initHeaders() {
-		if ( function_exists( 'apache_request_headers' ) ) {
-			$this->setHeaders( apache_request_headers() );
-		} else {
-			$headers = [];
-			foreach ( $_SERVER as $name => $value ) {
-				if ( substr( $name, 0, 5 ) === 'HTTP_' ) {
-					$name = strtolower( str_replace( '_', '-', substr( $name, 5 ) ) );
-					$headers[$name] = $value;
-				} elseif ( $name === 'CONTENT_LENGTH' ) {
-					$headers['content-length'] = $value;
-				} elseif ( $name === 'CONTENT_TYPE' ) {
-					$headers['content-type'] = $value;
-				}
-			}
-			$this->setHeaders( $headers );
-		}
+		$this->setHeaders( getallheaders() );
 	}
 
 	public function getBody() {
diff --git a/includes/WebRequest.php b/includes/WebRequest.php
index ecf355509ea..066b2239393 100644
--- a/includes/WebRequest.php
+++ b/includes/WebRequest.php
@@ -1089,21 +1089,7 @@ class WebRequest {
 			return;
 		}
 
-		$apacheHeaders = function_exists( 'apache_request_headers' ) ? apache_request_headers() : false;
-		if ( $apacheHeaders ) {
-			foreach ( $apacheHeaders as $tempName => $tempValue ) {
-				$this->headers[strtoupper( $tempName )] = $tempValue;
-			}
-		} else {
-			foreach ( $_SERVER as $name => $value ) {
-				if ( substr( $name, 0, 5 ) === 'HTTP_' ) {
-					$name = str_replace( '_', '-', substr( $name, 5 ) );
-					$this->headers[$name] = $value;
-				} elseif ( $name === 'CONTENT_LENGTH' ) {
-					$this->headers['CONTENT-LENGTH'] = $value;
-				}
-			}
-		}
+		$this->headers = array_change_key_case( getallheaders(), CASE_UPPER );
 	}
 
 	/**
diff --git a/tests/phpunit/includes/Rest/RequestFromGlobalsTest.php b/tests/phpunit/includes/Rest/RequestFromGlobalsTest.php
index 6be6128c51c..9a029ed5839 100644
--- a/tests/phpunit/includes/Rest/RequestFromGlobalsTest.php
+++ b/tests/phpunit/includes/Rest/RequestFromGlobalsTest.php
@@ -77,16 +77,26 @@ class RequestFromGlobalsTest extends MediaWikiTestCase {
 		$this->setServerVars( [
 			'HTTP_HOST' => '[::1]',
 			'CONTENT_LENGTH' => 6,
-			'CONTENT_TYPE' => 'application/json'
+			'CONTENT_TYPE' => 'application/json',
+			'CONTENT_MD5' => 'rL0Y20zC+Fzt72VPzMSk2A==',
 		] );
 
 		$this->assertEquals( $this->reqFromGlobals->getHeaders(), [
-			'host' => [ '[::1]' ],
-			'content-length' => [ 6 ],
-			'content-type' => [ 'application/json' ]
+			'Host' => [ '[::1]' ],
+			'Content-Length' => [ 6 ],
+			'Content-Type' => [ 'application/json' ],
+			'Content-Md5' => [ 'rL0Y20zC+Fzt72VPzMSk2A==' ],
 		] );
 	}
 
+	public function testGetHeaderKeyIsCaseInsensitive() {
+		$cacheControl = 'private, must-revalidate, max-age=0';
+		$this->setServerVars( [ 'HTTP_CACHE_CONTROL' => $cacheControl ] );
+
+		$this->assertSame( $this->reqFromGlobals->getHeader( 'Cache-Control' ), [ $cacheControl ] );
+		$this->assertSame( $this->reqFromGlobals->getHeader( 'cache-control' ), [ $cacheControl ] );
+	}
+
 	public function testGetBody() {
 		$this->setServerVars( [
 			'REQUEST_METHOD' => 'POST',
diff --git a/tests/phpunit/includes/WebRequestTest.php b/tests/phpunit/includes/WebRequestTest.php
index a0e89a18e97..50d5c25da18 100644
--- a/tests/phpunit/includes/WebRequestTest.php
+++ b/tests/phpunit/includes/WebRequestTest.php
@@ -644,6 +644,35 @@ class WebRequestTest extends MediaWikiTestCase {
 		$this->assertSame( $request->getAcceptLang(), $expectedLanguages, $description );
 	}
 
+	/**
+	 * @covers WebRequest::getHeader
+	 */
+	public function testGetHeaderCanYieldSpecialCgiHeaders() {
+		$contentType = 'application/json; charset=utf-8';
+		$contentLength = '4711';
+		$contentMd5 = 'rL0Y20zC+Fzt72VPzMSk2A==';
+		$this->setServerVars( [
+			'HTTP_CONTENT_TYPE' => $contentType,
+			'HTTP_CONTENT_LENGTH' => $contentLength,
+			'HTTP_CONTENT_MD5' => $contentMd5,
+		] );
+		$request = new WebRequest();
+		$this->assertSame( $request->getHeader( 'Content-Type' ), $contentType );
+		$this->assertSame( $request->getHeader( 'Content-Length' ), $contentLength );
+		$this->assertSame( $request->getHeader( 'Content-Md5' ), $contentMd5 );
+	}
+
+	/**
+	 * @covers WebRequest::getHeader
+	 */
+	public function testGetHeaderKeyIsCaseInsensitive() {
+		$cacheControl = 'private, must-revalidate, max-age=0';
+		$this->setServerVars( [ 'HTTP_CACHE_CONTROL' => $cacheControl ] );
+		$request = new WebRequest();
+		$this->assertSame( $request->getHeader( 'Cache-Control' ), $cacheControl );
+		$this->assertSame( $request->getHeader( 'cache-control' ), $cacheControl );
+	}
+
 	protected function setServerVars( $vars ) {
 		// Don't remove vars which should be available in all SAPI.
 		if ( !isset( $vars['REQUEST_TIME_FLOAT'] ) ) {