====== Debug Mode ======
~~NOTOC~~

<WRAP right box>
== Syntax ==
  $connection->debug = boolean|int;
</WRAP>

===== Description =====

Enabling debug mode makes the driver return debugging information from both ADOdb and the PHP driver itself.

The output includes the executed SQL statement with parameters, as well as error messages and backtrace information if there are problems.
It is suitable for viewing in a browser (see [[#formatting|Formatting section below]]) 

See [[v5:reference:logging]] for details on how to capture and redirect output.
===== Usage =====

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.
 
<code php>
include 'adodb.inc.php';
$conn = newAdoConnection('mysqli');

# Here is the earliest point where Debug Mode can be set

$conn->connect($host, $user, $pass, 'database');

# Enable Debug mode
$conn->debug = true;

$recordSet = $conn->execute('SELECT * FROM product');
</code>

The information returned on STDOUT is:
<code>
------------------------------------------------------------------------------
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
</code> 

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|Formatting section below]].

==== Possible values ====

In addition to the standard ''True'' and ''False'' states accepted by this switch, there are 3 additional non-boolean values that, if set, will vary some of the output produced.

^ Value  ^ Description                                                                                                     ^
| False  | Debug mode disabled (normal operations)                                                                         |
| True   | Standard mode, prints executed SQL statements and error information including a Backtrace if the query failed.  |
| -1     | Same as Standard mode, but with the line separators around the SQL statements suppressed.                       |
| 99     | Prints a Backtrace after every query execution, **even if the execution is successful**.                        |
| -99    | Debug information is only printed if query execution failed, reducing the amount of output.                     |


===== Formatting =====

Starting with ADOdb 5.23.0, debug output is printed with HTML markup and styled with CSS classes. This can be leveraged to improve display of various elements. 
The output's structure is as follows:

  * Wrapper ''div'' with //adodb-debug// class
    * **SQL statement** ''div'' with //adodb-debug-sql// class
      * Table with 2 columns (column 1 has ''th'' headers)
        * Row 1 with the query in a ''code'' block
        * Optional row 2 with the parameters in a ''code'' block, printed only there are any
    * **Error message** ''div'' if query execution failed, with //adodb-debug-errmsg// class
    * Code execution **backtrace** ''div'' with //adodb-debug-trace// class

Here is how the output looks like with the basic stylesheet below

{{ :v5:userguide:debug_output_styled.png?600 }}

<code css>
.adodb-debug-sql code {
    font-size: large;
}
.adodb-debug-errmsg {
    font-weight: bold;
    color: red;
}
.adodb-debug-trace table {
    border-spacing: 0;
    border: 1px solid;
}
.adodb-debug-trace thead {
    background-color: darkgray;
}
.adodb-debug-trace th, .adodb-debug-trace td {
    border: 1px solid;
    padding: 2px 6px;
}
</code>


===== Limitations =====

  * 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.

{{tag>[debugging]}}