Enabling debug mode makes the driver return copious amounts of debugging information from both ADOdb and the PHP driver itself. Information is displayed on both standard output (STDOUT) and standard error (STDERR) channels.

The debug option can be enabled and disabled at any time, to debug portions of a program. The earliest it can be set is after the inclusion of the driver, and before the connection.

In the following example, the table name is spelled incorrectly (it should be products). When run without debugging, the execution of the statement produces no output and simply returns false.

include 'adodb.inc.php';
$conn = newAdoConnection('mysqli');
$conn->connect($host, $user, $pass, 'database');
$conn->debug = true;
$recordSet = $conn->execute('SELECT * FROM product');

The information returned on STDOUT is:

------------------------------------------------------------------------------
mysqli: SELECT * FROM product
------------------------------------------------------------------------------
Query: select * from product failed. Table 'database.product' doesn't exist
1146: Table 'database.product' doesn't exist

Call stack (most recent call first):
 2. ADOConnection::_Execute(SELECT * FROM product) in .../drivers/adodb-mysqli.inc.php line 1091
 1. ADODB_mysqli::execute(SELECT * FROM product) in .../test.php line 36

By default, the parameters passed to the query are compressed into a set of key ⇒ value pairs. This information is printed after the SQL statement, using a <code> tag. Styling can be applied using CSS, see Formatting section below.

There are 3 non-boolean switches that, if set, will vary some of the output produced

• Historically, the output messages were coded to be sent to a web page and some contain formatting that may make the messages more difficult to read.
• Some drivers, the SQL server driver in particular, produce overwhelming volumes of debugging information.