<s>
Composer	O
is	O
an	O
application-level	O
dependency	O
manager	O
for	O
the	O
PHP	B-Application
programming	I-Application
language	I-Application
that	O
provides	O
a	O
standard	O
format	O
for	O
managing	O
dependencies	O
of	O
PHP	B-Application
software	O
and	O
required	O
libraries	B-Library
.	O
</s>
<s>
Composer	O
is	O
strongly	O
inspired	O
by	O
Node.js	B-Language
'	I-Language
s	I-Language
"	O
npm	B-Language
"	O
and	O
Ruby	B-Language
's	I-Language
"	O
bundler	O
"	O
.	O
</s>
<s>
The	O
project	O
's	O
dependency	O
solving	O
algorithm	O
started	O
out	O
as	O
a	O
PHP-based	O
port	O
of	O
openSUSE	O
's	O
libzypp	O
satsolver	O
.	O
</s>
<s>
Composer	O
runs	O
from	O
the	O
command	B-Application
line	I-Application
and	O
installs	O
dependencies	O
(	O
e.g.	O
</s>
<s>
libraries	B-Library
)	O
for	O
an	O
application	O
.	O
</s>
<s>
It	O
also	O
allows	O
users	O
to	O
install	O
PHP	B-Application
applications	O
that	O
are	O
available	O
on	O
"	O
Packagist	B-Library
"	O
which	O
is	O
its	O
main	O
repository	O
containing	O
available	O
packages	O
.	O
</s>
<s>
It	O
also	O
provides	O
autoload	O
capabilities	O
for	O
libraries	B-Library
that	O
specify	O
autoload	O
information	O
to	O
ease	O
usage	O
of	O
third-party	O
code	O
.	O
</s>
<s>
install	O
:	O
install	O
all	O
libraries	B-Library
from	O
composer.json	O
.	O
</s>
<s>
It	O
's	O
the	O
command	O
to	O
use	O
to	O
download	O
all	O
PHP	B-Application
repository	O
dependencies	O
.	O
</s>
<s>
update	O
:	O
update	O
all	O
libraries	B-Library
from	O
composer.json	O
,	O
according	O
to	O
the	O
allowed	O
versions	O
mentioned	O
into	O
it	O
.	O
</s>
<s>
The	O
different	O
authorized	O
versions	O
of	O
the	O
libraries	B-Library
are	O
defined	O
by	O
:	O
</s>
<s>
"	O
php	B-Application
"	O
:	O
"	O
>=	O
5.5.9	O
"	O
includes	O
PHP	B-Application
7	O
.	O
</s>
<s>
"	O
symfony/symfony	O
"	O
:	O
"	O
3.1	O
.	O
</s>
<s>
^	O
same	O
as	O
tilde	O
,	O
only	O
if	O
there	O
is	O
a	O
backward	B-General_Concept
compatibility	I-General_Concept
.	O
</s>
