php-guestbook/persistence.php

<?php

function createDB($db_name = 'guestbook.db'): SQLite3 {
	// Can't create table if it already exists
	$exists = file_exists($db_name);

	$db = new SQLite3($db_name);

	if(!$exists) {
		$db->exec('CREATE TABLE user
					(id_user INTEGER PRIMARY KEY,
					username TEXT NOT NULL UNIQUE,
					password TEXT)'
		);
		$db->exec('CREATE TABLE message
					(id_msg INTEGER PRIMARY KEY,
					id_user INT,
					content TEXT NOT NULL,
					date INT,
					FOREIGN KEY (id_user) REFERENCES user (id_user))'
		);
	}

	return $db;
}

function getMessages(SQLite3 $db, array $filter = [], int $limit = 25) {
	// Apply filters
	$append_string = '';
	$verb = 'WHERE';

	foreach($filter as $key => $value) {
		$to_append = match($key) {
			'id_user' => "$verb $key = :$key",
			// TODO
		};
		if($to_append) {
 			$append_string .= " $to_append";
			$verb = 'AND';
		}
	}

	// Prepare statement
	$query = 'SELECT * FROM message' . $append_string;
	//var_dump($query);

	$statement = $db->prepare($query);

	foreach($filter as $key => $value) {
		$statement->bindParam($key, $value);
	}

	$result = $statement->execute();

	$notnull = true;
	$ret = [];
	while($notnull) {
		$arr = $result->fetchArray(SQLITE3_ASSOC);
		//var_dump($arr);
		if($arr !== false) {
			$ret[] = $arr;
		}
		else $notnull = false;
	}

	return $ret;
}

function storeMessage(SQLite3 $db, string $content, ?int $user_id = null) {
	$query = 'INSERT INTO message(id_user, content, date) VALUES (:id_user, :content, :date)';
	$date = (new DateTime('now'))->getTimestamp();
	$statement = $db->prepare($query);
	$statement->bindParam(':id_user', $user_id);
	$statement->bindParam(':content', $content);
	$statement->bindParam(':date', $date);
	$statement->execute();
}