WEBVTT

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Profiling a page looks like this.

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First, something tells the Blackfire
PHP extension - the "Probe": Hey!

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Start profiling!

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Which basically means that it
starts collecting tons of data.

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The process of collecting data
is called instrumentation...

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because when a concept is too simple, sometimes
we tech people like to invent confusing words.

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Instrumentation means that the
PHP extension is collecting data.

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The second step is that - eventually -
something tells the PHP extension to stop

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"instrumentation" and to send the data.

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The collection of data is known as a "profile".

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The PHP extension sends the profile to the
agent, which aggregates it, prune some stuff

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and ultimately sends it to the Blackfire server.

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So: what is the "thing" that tells
the PHP extension to activate?

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We know that the PHP extension
doesn't profile every request...

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so what is it that says: Hey PHP
extension "probe" thing: start profiling!

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The answer - so far - is: the browser
extension: it sends special information

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that tells the probe to do its thing.

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Or, if you use the blackfire command
line utility, which we did earlier

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to profile a command, then it is what
tells the PHP extension to activate.

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In either situation, the extension is activated
before even the first line of code is executed.

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That means that every single line
of PHP code is "instrumented":

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our final profile contains everything.

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This is called auto-instrumentation:
instrumentation starts automatically.

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This naturally leads to three
interesting questions.

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First, who is baby Yoda?

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I mean, is he...

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like, related to Yoda?

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Or just the same species?

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The second question is: could we trigger, or
create a Blackfire profile in a different way?

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Could we, for example, dynamically tell
the PHP extension to create a profile

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from inside our code under
some specific condition?

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And third, regardless of who triggers
the profile, could we "zoom in"

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and only collect profiling
data for part of our code?

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Like, could we create a profile that
only collects data about the code

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from our controller instead
of the entire request?

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Let's actually start with that last
question: profiling a specific part

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of our code, instead of the whole thing.

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To be fully honest, I don't know if this
part has a ton of practical use-cases,

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but it will give you an even better idea
of how Blackfire works behind the scenes.

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To help with this crazy experiment, we're
going to install Blackfire's PHP SDK.

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Find your terminal, dial up your
modem to the Internet, and run:

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composer require blackfire/php-sdk This is a
normal PHP library that helps interact directly

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with Blackfire from inside your code.

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You'll see how.

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When it finishes, move over and open
src/Controller/MainController.php.

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Ok: this is the controller for our homepage.

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Let's pretend that when we profile this page,

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we don't want to collect
data about all of our code.

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Nope, we want to, sort of, "zoom in" and see
only what's happening inside the controller.

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We can do that by saying $probe =
\BlackfireProbe::getMainInstance().

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Remember: the PHP extension
is called the "probe"...

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that's important if you want this to make sense.

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Then call $probe->enable().

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At the bottom, I'll set the rendered template
to a $response variable, add $probe->disable()

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and finish with return $response.

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Okay, so...

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what the heck does this do?

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The first thing I want you to notice is that
if I refresh the homepage a bunch of times...

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and then go to https://blackfire.io,
I do not have any new profiles.

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Adding this code does not "trigger"
a new profile to be created:

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it does not tell the PHP extension - the
"probe" - that it should to do its work.

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Instead, if a profile is
currently being created,

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this tells the probe when
to start collecting data.

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Hmm, this isn't going to quite make
sense until we see it in action.

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Trigger a new profile on the homepage.

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I'll call this one: [Recording]
Only instrument some code.

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Click to view the call graph:
https://bit.ly/sf-bf-partial-profile.

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Fascinating.

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This contains less information than normal.

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It has a few things on top
- main() and handleRaw()...

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but basically it jumps straight
to the homepage() method.

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What's happening here is that the only
code that the probe "instrumented",

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the only code that it collected information on,

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is the code between the enable()
and disable() calls.

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This... completely confused
me the first time I saw it.

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What really happens is this: as soon as we
use the browser extension to tell the probe

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to do its job, the PHP extension
starts instrumenting -

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so, collection data - immediately.

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Initially, it is collecting data
about every line of PHP code.

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But as soon as it sees $probe->enable(),
it basically forgets

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about all the data collected so far.

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The $probe->enable() call says: Hey!

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Start instrumenting here.

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If you've already collected some data before
thanks to auto-instrumentation, get rid of it.

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This effectively disables
auto-instrumentation: we're now controlling

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which code is instrumented instead
of it happening automatically.

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Once the code hits $probe->disable()
instrumentation stops.

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You can actually use $probe->enable() and
$probe->disable() multiple times in your code

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if you want to profile different pieces:

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$probe->enable() only forgets data it's
already collected the first time you call it.

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Oh, and you can also optionally
call $probe->close() -

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you'll see this in their documentation.

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That tells the PHP extension that
you're definitely done profiling

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and it can send the data to the agent.

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But, it's not strictly required,
because it'll be sent automatically

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when the script ends anyways.

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So... this feature is maybe useful...

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but it's definitely a nice intro into taking
more control of the profiling process.

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And.. fun fact!

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We installed the blackfire/php-sdk library...

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but we haven't actually used it yet!

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This \BlackfireProbe class is
not from the php-sdk library:

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it's from the Blackfire PHP extension.

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As long as you have the extension
installed, that class will exist.

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We're interacting directly with the extension.

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So... why did we install the
SDK if we didn't need it?

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Because...

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it gave us auto-complete on that class.

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And you all know that I freakin'
love auto-complete.

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The SDK has a, sort of, "stub"
version of this class.

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This is not the code that was actually
executed when we called those methods...

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but having this at least shows us
what methods and arguments exist.

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Next, let's actually use the PHP SDK
to do something a bit more interesting.

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I want to create a profile
automatically in my code

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without needing to use the browser extension.

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This does have real-world use-cases.