PDO PHP SQLite3数据库连接常规错误14

Question

I have 2 sqlite3.x databases (from an iPhone), one from a game app, and the other is the address book.

I have logging and display errors 'on' in the php conf.

Using PHP/PDO I can display the fields and values from the game database, including image blobs which I catch with my results page and render with "img src='data:...'. I'm using htmlentities on other fields to catch things like plist binary blobs.

I'm using a perl script to generate the first page, and the sample data is obtained using a system call to sqlite3. The script is doing a recursive search through a directory provided as a cli argument.

I basically get the first record from each table within a database (as a data sample), give the user options on which fields they want to further interrogate, and pass those options to a form handler which executes the query against the target table, and getting data from the chosen columns.

However...I get a "unable to open database" general error when trying to connect to the addressbook database.

I have checked the database permissions, ownership, put both in the same directory, made them fully open to the world..everything I can think of, and still no joy.

What's really odd is that I can query all databases quite happily from the commandline with sqlite3, but get this error when using PDO.

The whole things trips up at the following:

($db and $strSQL vals passed from previous page)

$dbh = new PDO('sqlite:'.$db);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
$result = $dbh->query($strSQL);

Even if I select a simple primary key column from the table, I get the error, so I'm pretty sure it's not a data handling problem. I've even tried this same script against Firefox and Chrome databases...no problems at all.

Would really appreciate any ideas/pointers/suggestions. This one is doing my head in!

Cheers.

Answer 1

OK...So it seems that despite the fact the database files themselves were wide open (chmod 777), the directory where they sit has to be writeable! Still not sure how sqlite from the commandline gets away with not requiring a writable directory, but you certainly need it for PHP/PDO queries.

The databases that were not showing results have the Write-Ahead Logging (WAL) bits set (bytes 18 and 19 of the file header), and the directory needs to be writeable so SQLite can create the WAL version of the database being queried. Bytes 18 and 19 are set to 0x01 and 0x01 for non-WAL dbs, and 0x02 0x02 for WAL enabled databases.

What gave it away?...the sudden appearance of copies of my addressbook database file with "-wal" and "-shm" appended to the end of the filename when I re-ran the query and happened to have moved the DBs into a writeable directory for testing.

Go figure!

PS.. Interestingly enough, every time the journal mode is changed (using a db query "pragma journal_mode=[wal|off]"), a 2 byte counter at bytes 94 and 95 increments by one. Noted this when checking the hash values of the db when flipping between modes, and could not get the same 2 hashes. I did a xxd on a before and after database, piped the output to txt files, then diff'd the 2 txt files...and there were these counter bytes.

Answer 2

Based on the error message "Unable to open Database", it's unable to access the sqlite file. I am sure you have checked your "$db" variable from previous page.

It's difficult to give you a definite answer. Can you try without PDO, just to check wether there is an issue with sqlite file or the PHP code.

Post your results and lets see.