functions.php: add has_any_history function

inc/functions.php

@@ -918,6 +918,26 @@ function checkBan($board = false) {
 	}
 }
 
+/**
+ * Checks if the given IP has any previous posts.
+ *
+ * @param string $ip The IP to check.
+ * @return bool True if the ip has already sent at least one post, false otherwise.
+ */
+function has_any_history(string $ip): bool {
+	foreach (listBoards(true) as $board_uri) {
+		$query = prepare(sprintf('SELECT `id` FROM ``posts_%s`` WHERE `ip` = :ip LIMIT 1', $board_uri));
+		$query->bindValue(':ip', $ip);
+		$query->execute() or error(db_error());
+
+		if ($query->fetchColumn() !== false) {
+			// Found a post.
+			return true;
+		}
+	}
+	return false;
+}
+
 function threadLocked($id) {
 	global $board;