Marcus Downing

Enable system logging for WordPress plugin and theme development. This can make it easier to know what your code is doing.
Features include:
<ul>
<li>Log to the system log or to a file</li>
<li>Easily append or embed any value in log messages</li>
<li>Coloured logs indicating strings, numbers, arrays, objects, null values etc.</li>
<li>Extract values from arrays of objects</li>
<li>Optionally exclude AJAX, Javascripts, CSS and any other pattern of URLs.</li>
<li>Intercept PHP errors and log strict warnings</li>
<li>Measure memory usage between two points, or the time taken by various parts of your code</li>
<li>Easy to switch off for production sites</li>
</ul>
<h4>How to use</h4>
Using it is as simple as calling the <code>'log'</code> action in your templates or plugin.
<pre><code><?php do_action('log', 'Some log message'); ?>
</code></pre>
This will produce a line in your system log:
<pre><code>Jun 4 11:23:08 myserver php/mysite.com[1553]: b8e mysite.com/path-to-page: Some log message
</code></pre>
This includes:
<ul>
<li><code>Jun 4 11:23:08</code> – The date and time of the log message</li>
<li><code>myserver</code> – The name of this computer</li>
<li><code>php</code> – The program that produced the message</li>
<li><code>mysite.com</code> – The domain name of the site</li>
<li><code>1553</code> – The process ID of the running PHP process</li>
<li><code>b8e</code> – A random 3-digit code identifying each page request</li>
<li><code>mysite.com/path-to-page</code> – The URL of the request</li>
<li><code>Some log message</code> – Your message</li>
</ul>
For more detailed instructions, see the How to use tab.
<h3>How to use</h3>
To log a message, use the <code>'log'</code> action in your templates or plugins:
<pre><code><?php do_action('log', 'Some log message'); ?>
</code></pre>
This will output the log message:
<pre><code>Some log message
</code></pre>
<h4>Embedding values</h4>
If you include extra parameters, they’ll be added at the end of the log message:
<pre><code><?php do_action('log', 'A number and a string', 17, 'foo'); ?>
</code></pre>
This will produce the log message:
<pre><code>A number and a string: 17, foo
</code></pre>
The value will be formatted correctly depending on its type: integers, strings, arrays, objects, booleans etc. 
You don’t need to check if values are null or empty, they’ll still be output safely.
If you put the code <code>%s</code> into your log message, then one of the arguments will be dropped into the message:
<pre><code><?php do_action('log', 'I have %s numbers', count($numbers), $numbers); ?>
</code></pre>
This will produce the log message:
<pre><code>I have 4 numbers: [9, 16, 307, 1]
</code></pre>
<h4>Selecting fields</h4>
Logging a complete object – such as a WordPress post – can be very large, and sometimes it’s only one or two fields you need. 
If you put a string starting with an exclamation point <code>"!"</code> followed by a list of field names, they will be selected from the following object. 
The following will only show the <code>ID</code> and <code>post_title</code> fields of the post:
<pre><code><?php do_action('log', 'Loaded the post', '!ID,post_title', $post); ?>
</code></pre>
This will produce the log message:
<pre><code>Loaded the post: {ID: 1932, post_title: Test page}
</code></pre>
If you do this with an array of objects, those fields will be selected from each of them. The following will output a list of post <code>ID</code>s:
<pre><code><?php do_action('log', 'Loaded %s posts', count($posts), '!ID', $posts); ?>
</code></pre>
This will produce the log message:
<pre><code>Loaded 3 posts: [1932, 1594, 1103]
</code></pre>
<h4>Coloured logs</h4>
If you have coloured logging switched on, values will appear in different colours to indicate their type. 
This can make for quicker scanning of log files. 
To enable coloured logs, tick the Coloured logs checkbox on the settings page. 
Then use the <code>log.sh</code> script, included with this plugin, to decode and display the coloured log files.

Bang System Logging

Enable system logging for WordPress plugin and theme development.

Daniel Cid

The Trunc Logging plugin gives you visibility to all the activity inside WordPress. Logins, logouts, failed logins, new posts, new 
plugins, etc. Every major activity from WordPress is stored for analysis and forensics purposes.
Tracked actions:
<ul>
<li>Logins</li>
<li>Failed logins</li>
<li>Posts / pages published</li>
<li>Posts / pages trashed</li>
<li>Posts / pages removed</li>
<li>Plugin installed</li>
<li>Plugin activated</li>
<li>Themes installed</li>
<li>Themes activated</li>
</ul>
And much more.

Trunc Logging – Auditing syslog for WordPress


Maybe a biased review, but I use it on all my sites. Nothing better than having good logging showing all of what is happening inside WordPress. 


Use it on all my sites

The Trunc Logging plugin gives you visibility to all the activity inside WordPress. Logins, logouts, failed logins, new posts, new plugins, etc.

Bang System Logging vs Trunc Logging – Auditing syslog for WordPress