This function behaves identically to sqlite_open() except that is uses the persistent resource mechanism of PHP. For information about the meaning of the parameters, read the sqlite_open() manual page.
sqlite_popen() will first check to see if a persistent handle has already been opened for the given filename. If it finds one, it returns that handle to your script, otherwise it opens a fresh handle to the database.
The benefit of this approach is that you don't incur the performance cost of re-reading the database and index schema on each page hit served by persistent web server SAPI's (any SAPI except for regular CGI or CLI).
If you use persistent handles and have the database updated by a background process (perhaps via a crontab), and that process re-creates the database by overwriting it (either by unlinking and rebuilding, or moving the updated version to replace the current version), you may experience undefined behaviour when a persistent handle on the old version of the database is recycled.
To avoid this situation, have your background processes open the same database file and perform their updates in a transaction.
The filename of the SQLite database. If the file does not exist, SQLite will attempt to create it. PHP must have write permissions to the file if data is inserted, the database schema is modified or to create the database if it does not exist.
The mode of the file. Intended to be used to open the database in
read-only mode. Presently, this parameter is ignored by the sqlite
library. The default value for mode is the octal value
0666 and this is the recommended value.
Passed by reference and is set to hold a descriptive error message explaining why the database could not be opened if there was an error.