Database locked while trying to access from PHP script

First, when you are done with a resource you should always close it. In theory it will be closed when it is garbage-collected, but you can't depend on PHP doing that right away. I've seen a few databases (and other kinds of libraries for that matter) get locked up because I didn't explicitly release resources.

$db->close();unset($db);

Second, Sqlite3 gives you a busy timeout. I'm not sure what the default is, but if you're willing to wait a few seconds for the lock to clear when you execute queries, you can say so. The timeout is in milliseconds.

$db->busyTimeout(5000);

I was getting "database locked" all the time until I found out some features of sqlite3 must be set by using SQL special instructions (i.e. using PRAGMA keyword). For instance, what apparently solved my problem with "database locked" was to set journal_mode to 'wal' (it is defaulting to 'delete', as stated here: https://www.sqlite.org/wal.html (see Activating And Configuring WAL Mode)).

So basically what I had to do was creating a connection to the database and setting journal_mode with the SQL statement. Example:

<?php  $db = new SQLite3('/my/sqlite/file.sqlite3');  $db->busyTimeout(5000);  // WAL mode has better control over concurrency.  // Source: https://www.sqlite.org/wal.html  $db->exec('PRAGMA journal_mode = wal;');?>

Hope that helps.