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Composer plays another important role by
helping us maintain package versioning.

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This feature has a couple
important benefits.

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First, it allows us to stay
current on any security updates

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to external packages that we're
using in our application.

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Second, it allows us to easily upgrade
as new features become available.

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So how does versioning work and how do
we use composer to maintain versioning?

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Composer version control is built
around a standard versioning system

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called semantic versioning.

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Under this system, version numbers and
the way they change convey meaning about

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the underlying code and what has been
modified from one version to the next.

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The first position signifies major changes

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that break the way things
work in the previous version.

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The second position signifies minor
changes such as new features that

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add functionality without
changing current functionality.

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And finally, the third position
signifies patches such as bug fixes or

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security updates.

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Incrementing on any of these
numbers signifies a change.

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Let's take P.H.P.
for example in September of

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2016 P.H.P. released version 7.0.11.

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7 stands for the major version,

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0 is the minor version, and
11 is the current patch.

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As a general rule, upgrading to a minor
release or patch within the same

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major release should be backwards
compatible and not break any of your code.

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This standard is widely accepted,

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however, not every package you use is
guaranteed to follow these guidelines.

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So it's a good idea to check with
the package you wish to use.

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Let's now go see package versioning
in action with composer.

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Let's start by taking a look
at what we already have.

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We use the command line to install
packages up to this point.

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Composer uses a composer.json file for
configuration and

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you can modify this file manually.

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When we open the file, you can see
the four packages we installed, but

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not their dependencies.

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Composer handles the package
dependencies for us.

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You can add, remove and change packages
and versions directly in this file.

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Next to each package is a version number.

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Notice how they only have two positions
and there is a carrot at the beginning.

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This defines the minimum
required version and

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allows composer to perform any minor or
patch updates.

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This also prevents composer from
upgrading to the next major version.

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Composer gives you many different
options for controlling versions.

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For example, I can change the caret
to a Tilde in the HTML purifier.

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I get the same results because
using a tilde will increment

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the last number given.

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However, if I specify tilde 4.8.0,

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it would only increment the patch version.

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While using caret 4 .8.0 will increment
both the patch and the minor version.

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Check out the notes
associated with this video

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to learn more about options and tools.

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When you make changes to
your composer.json file,

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those changes will not take effect
until you run a composer update.