Strategies for Debugging in Xaraya

There are numerous types of bugs and ways the manifest themselves. Some examples,

• Logic errors in template -- not seeing the output you expected
• Block layout syntax error -- you get an error page with the template name and line number
• "white page of death" -- usually indicates a php syntax error
• Lots of missing content -- like the "white page" but you lose only one template

The white page can be caused by (just some examples I can think of):

• missing #, such as <p>#$body</p>
  
• missing closing parenthesis, such as <xar:set name="arts">xarModApiFunc('articles','user','get', array('aid'=>'14')</xar:set>
• invalid syntax within #'s, such as #$item['title'])# (the parenthesis causes white death)
  

Dumping Variables from a Template

print_r()

To dump a variable to the current page:

<pre><xar:set name="asdf">print_r($var)</xar:set></pre>

If things are really messing up, you can stop the output generation (die) immedately after the dump:

<pre><xar:set name="asdf">print_r($var); die()</xar:set></pre>

var_dump()

Like print_r() but also shows the value "types" (int, array, etc).

dump into comments

If you prefer to not mess up your page (especially on a live site), you can output the dump as an html comment. BL doesn't like us using xar:set with a value that looks like a comment :) so you have to work around with an embedded php hack

<xar:set name="asdf">1; $opencomment="<!-- "; $closecomment=" -->";</xar:set>

#$opencomment#

The value of $var is #$var#

#$closecomment#

Error Logs

var/logs/log.txt

When things look like they're not going well, be sure to check your Xaraya log file. By default, there is no logging. To start debug logging, simply touch (create 0 length file) at var/logs/log.txt . And make sure it is web-server writeable (e.g. permissions 774)

The file contains a trace log of everything you do when loading each page. Ignore most of it, just look for ERRORs rather than DEBUG statements.

To stop logging, delete the file.

php error log

You might want to turn on php error logging. That's set in the php.ini file.

log_errors = on

and something like

; Log errors to specified file.
error_log = php_error.log

If you dont specify a path, it will (should) write it into the current web root. You can also tell php to output it as html so you can view it in your browser, though I dont use that.

Cache

One source of frustration is when you think you've fixed something but its still broken.

Clear template cache

from command line:

rm -f var/cache/templates/*.php CACHEKEYS

or from the SiteTools module.

Clear browser cache

yup.

Clear session cookies

This can be helpful for example if there's session vars hanging around and you want to start fresh. The FireFox webdeveloper plugin can do this directly.

Debugging PHP

Even if you're not a module developer, you sometimes might need to trace through the php code to see what's going on or help track down a bug.

You can output directly to the current page using echo, print_r(), printf(), and var_dump() . Note, these will also cause a warning message on your page that you have output that has not gone through the normal buffering. Examples:

echo 'you have entered articles_userapi_getall';

printf( "the value of x is %s", $x );

print_r( $arr );

var_dump( $arr );

Output to log.txt

To send your debugging info to log.txt instead of the page:

xarLogMessage( $string );

xarLogVariable($name, $var );

for example,

xarLogMessage( 'entered articles_userapi_getall');
xarLogVariable('args', $args);

I suppose these functions can be called from a template too though I havent had occation to do that yet.

Using xdebug

Disclaimer, i've never tried they yet myself, but dropped these notes in here. One day I'll give it a try and update this section.

in php.ini:

extension=xdebug.so
xdebug.collect_params=1
xdebug.collect_return=1
xdebug.trace_output_name=timestamp

in template:

<xar:set name="dummy1">1;xdebug_start_trace()</xar:set>

...

<xar:set name="dummy2">1;xdebug_stop_trace()</xar:set>