[php] Add extern for `mime_content_type()` (#9835)

std/php/Global.hx

@@ -1546,6 +1546,11 @@ extern class Global {
 	**/
 	static function gzuncompress(data:String, ?length:Int):EitherType<String, Bool>;
 
+	/**
+		@see http://php.net/manual/en/function.mime-content-type.php
+	**/
+	static function mime_content_type(filename:String):EitherType<String, Bool>;
+
 	/**
 		@see http://php.net/manual/en/function.move-uploaded-file.php
 	**/