The Debug component provides an API to log and time debug events. This
component depends mainly on the EventLog component. The functionality of the
Debug component is divided into two parts:
- Writing debug messages.
- Measuring the execution time.
Writing a debug message is almost the same as writing a message with the
EventLog component. However, there is one major distinction: messages written
with the EventLog component are intended to be written to a storage element
(such as a log file or database). Messages written with the Debug component are
usually directly formatted and displayed. Note that the Debug::log() method has
a slightly different signature than the EventLog::log() method.
Timing information is captured by starting and stopping timers using the public
methods from ezcDebug. The timing information is stored in a structure with raw
data. This structure should be formatted and displayed at the end of the
script.
The Debug summary output can be formatted with an implementation from
ezcDebugOutputFormatter. The default, and currently only, formatter is
ezcDebugHtmlFormatter. This HTML formatter transforms the raw log
messages and raw timing information into a HTML string for display.
The following script writes a message to the Debug component. At the end of the
script, the log message is formatted and printed.
1. <?php
2.
3. require_once 'tutorial_autoload.php';
4. date_default_timezone_set( "UTC" );
5.
6. // Get the one and only instance of the ezcDebug.
7. $debug = ezcDebug::getInstance();
8.
9. // Write a log message with verbosity 1.
10. $debug->log( "Connecting with the Payment server", 1 );
11.
12. $debug->log( "Connected with the Payment server", 2, array( "source" => "shop", "category" => "payment" ) );
13.
14. // Get HTML output.
15. $output = $debug->generateOutput();
16.
17. echo $output;
18. ?>
Writing log messages is almost the same as writing them to the EventLog
component. As a matter of fact, the EventLog component is internally used by
Debug.
Further information about writing log messages can be found in the EventLog
component.
The timers from ezcDebug can be used for two purposes:
- Timers measure the time between two points in the program.
- Accumulators get the current time after a certain point (for example after
starting the script).
Both methods are executed with ezcDebug::startTimer(), ezcDebug::stopTimer()
and ezcDebug::switchTimer(). The next script demonstrates the usage of these
methods:
1. <?php
2.
3. require_once 'tutorial_autoload.php';
4. date_default_timezone_set( "UTC" );
5.
6. // Get the one and only instance of the ezcDebug.
7. $debug = ezcDebug::getInstance();
8.
9. // Start the accumulator.
10. $debug->startTimer( "Program runtime", "Accumulators" );
11. $debug->switchTimer( "Start", "Program runtime" );
12.
13. // Measure the time of writing "hello world".
14. // The name of the timer is: "Hello world" and it will be placed in the group: "output".
15. $debug->startTimer ("Hello world", "output" );
16. echo "Hello world<br/>";
17. $debug->stopTimer( "Hello world" );
18.
19. // Replace the "Start" timer for "Half the way".
20. $debug->switchTimer( "Half the way", "Start" );
21.
22. // Measure the time of writing "cruel world".
23. $debug->startTimer( "Goodbye cruel world", "output" );
24. echo "Goodbye cruel world<br/>";
25. $debug->stopTimer( "Goodbye cruel world" );
26.
27. // Stop the last timer.
28. $debug->switchTimer( "Stop", "Half the way" );
29. $debug->stopTimer( "Stop" );
30.
31. // Get HTML output.
32. $output = $debug->generateOutput();
33.
34. echo "<br/><br/>";
35. echo $output;
36. ?>
The output is as follows:
The output has two groups: output and accumulators. There are two timers in the
"output" group: "Hello world" and "Goodbye cruel world".
The "accumulators" group has one timer called "Program runtime". This
timer took a total of 0.00034 seconds. In this timer are several "switch
timers". These show the time since the "Program runtime" was started.
You can also time repeating code blocks. For example, you can measure the time a
PHP statement takes in a loop. The Debug timer will calculate the average time
of the repeating statement and display it in the debug summary. See the next
example:
1. <?php
2.
3. require_once 'tutorial_autoload.php';
4. date_default_timezone_set( "UTC" );
5.
6. // Get the one and only instance of the ezcDebug.
7. $debug = ezcDebug::getInstance();
8.
9. // Start the accumulator.
10. $debug->startTimer( "Script runtime", "Accumulators" );
11.
12. // Store the name of the accumulator.
13. $accumulatorName = "start";
14. $debug->switchTimer( $accumulatorName, "Script runtime" );
15.
16. // Time the loop.
17. $debug->startTimer ( "Five times Hello world", "output" );
18. for( $i = 0; $i < 5; $i++ )
19. {
20. // Time the "Hello world" only.
21. $debug->startTimer ( "Hello world", "output" );
22. echo "Hello world<br/>";
23. $debug->stopTimer( "Hello world" );
24.
25. // Store the accumulator.
26. $debug->switchTimer( "After: hello world", $accumulatorName );
27. $accumulatorName = "After: hello world";
28. }
29. $debug->stopTimer( "Five times Hello world" );
30.
31. // Stop the accumulator
32. $debug->switchTimer( "stop", $accumulatorName );
33. $debug->stopTimer( "stop" );
34.
35. // Get HTML output.
36. $output = $debug->generateOutput();
37.
38. echo "<br/><br/>";
39. echo $output;
40.
41. ?>
The resulting output is as follows:
