<s>
HipHop	B-Language
Virtual	I-Language
Machine	I-Language
(	O
HHVM	B-Language
)	O
is	O
an	O
open-source	B-Application
virtual	B-Architecture
machine	I-Architecture
based	O
on	O
just-in-time	O
(	O
JIT	O
)	O
compilation	O
that	O
serves	O
as	O
an	O
execution	O
engine	O
for	O
the	O
Hack	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
By	O
using	O
the	O
principle	O
of	O
JIT	O
compilation	O
,	O
Hack	B-Language
code	O
is	O
first	O
transformed	O
into	O
intermediate	O
HipHop	B-Language
bytecode	I-Language
(	O
HHBC	B-Language
)	O
,	O
which	O
is	O
then	O
dynamically	O
translated	O
into	O
x86-64	B-Device
machine	B-Language
code	I-Language
,	O
optimized	B-Application
,	O
and	O
natively	O
executed	O
.	O
</s>
<s>
This	O
contrasts	O
with	O
PHP	B-Application
's	O
usual	O
interpreted	B-Application
execution	O
,	O
in	O
which	O
the	O
Zend	B-Language
Engine	I-Language
transforms	O
PHP	B-Application
source	O
code	O
into	O
opcodes	B-Language
that	O
serve	O
as	O
a	O
form	O
of	O
bytecode	O
,	O
and	O
executes	O
the	O
opcodes	B-Language
directly	O
on	O
the	O
Zend	B-Language
Engine	I-Language
's	O
virtual	O
CPU	B-Device
.	O
</s>
<s>
HHVM	B-Language
is	O
developed	O
by	O
Meta	O
,	O
with	O
the	O
project	O
's	O
source	O
code	O
hosted	O
on	O
GitHub	B-Application
;	O
it	O
is	O
licensed	O
under	O
the	O
terms	O
of	O
the	O
PHP	B-Language
License	I-Language
and	O
Zend	O
License	O
.	O
</s>
<s>
HHVM	B-Language
was	O
created	O
as	O
the	O
successor	O
to	O
the	O
HipHop	B-Language
for	I-Language
PHP	I-Language
(	O
HPHPc	B-Language
)	O
PHP	B-Application
execution	O
engine	O
,	O
which	O
is	O
a	O
PHP-to-C	O
++	O
transpiler	B-Language
also	O
created	O
by	O
Facebook	B-Application
.	I-Application
</s>
<s>
Based	O
on	O
the	O
gained	O
experience	O
and	O
aiming	O
to	O
solve	O
issues	O
introduced	O
by	O
HPHPc	B-Language
,	O
Meta	O
decided	O
in	O
early	O
2010	O
to	O
create	O
a	O
JIT-based	O
PHP	B-Application
virtual	B-Architecture
machine	I-Architecture
.	O
</s>
<s>
Issues	O
associated	O
with	O
HPHPc	B-Language
included	O
reaching	O
a	O
plateau	O
for	O
further	O
performance	O
improvements	O
,	O
a	O
fundamental	O
inability	O
to	O
support	O
all	O
features	O
of	O
the	O
PHP	B-Application
language	I-Application
,	O
and	O
difficulties	O
arising	O
from	O
specific	O
time	O
-	O
and	O
resource-consuming	O
development	O
and	O
deployment	O
processes	O
.	O
</s>
<s>
In	O
Q12013	O
,	O
the	O
production	O
version	O
of	O
the	O
facebook.com	O
website	O
stopped	O
using	O
HPHPc	B-Language
and	O
switched	O
to	O
HHVM	B-Language
.	O
</s>
<s>
Following	O
the	O
JIT	O
compilation	O
principle	O
,	O
HHVM	B-Language
first	O
converts	O
the	O
executed	O
code	O
into	O
an	O
intermediate	O
language	O
,	O
the	O
high-level	O
bytecode	O
HHBC	B-Language
.	O
</s>
<s>
HHBC	B-Language
is	O
a	O
bytecode	O
format	O
created	O
specifically	O
for	O
HHVM	B-Language
,	O
appropriate	O
for	O
consumption	O
by	O
both	O
interpreters	B-Application
and	O
just-in-time	O
compilers	O
.	O
</s>
<s>
Next	O
,	O
HHVM	B-Language
dynamically	O
(	O
"	O
just-in-time	O
"	O
)	O
translates	O
the	O
HHBC	B-Language
into	O
x86-64	B-Device
machine	B-Language
code	I-Language
,	O
optimized	B-Application
through	O
dynamic	O
analysis	O
of	O
the	O
translated	O
bytecode	O
.	O
</s>
<s>
Finally	O
,	O
it	O
executes	O
the	O
x86-64	B-Device
machine	B-Language
code	I-Language
.	O
</s>
<s>
As	O
a	O
result	O
,	O
HHVM	B-Language
has	O
certain	O
similarities	O
to	O
the	O
virtual	B-Architecture
machines	I-Architecture
used	O
by	O
other	O
programming	O
languages	O
,	O
including	O
the	O
Common	O
Language	O
Runtime	O
(	O
CLR	O
,	O
for	O
the	O
C#	B-Application
language	O
)	O
and	O
Java	B-Language
virtual	I-Language
machine	I-Language
(	O
JVM	B-Language
,	O
for	O
the	O
Java	B-Language
language	I-Language
)	O
.	O
</s>
<s>
HHVM	B-Language
brings	O
many	O
benefits	O
in	O
comparison	O
with	O
HPHPc	B-Language
.	O
</s>
<s>
HHVM	B-Language
uses	O
the	O
same	O
execution	O
engine	O
when	O
deployed	O
in	O
both	O
production	O
and	O
development	O
environments	O
,	O
while	O
supporting	O
integration	O
between	O
the	O
execution	O
engine	O
and	O
the	O
HPHPd	B-Language
debugger	B-Application
in	O
both	O
environment	O
types	O
;	O
as	O
a	O
result	O
,	O
maintaining	O
HPHPi	B-Language
(	O
HipHop	B-Language
interpreter	B-Application
)	O
separately	O
as	O
a	O
development	O
utility	O
is	O
no	O
longer	O
needed	O
as	O
it	O
was	O
the	O
case	O
with	O
HPHPc	B-Language
.	O
</s>
<s>
HHVM	B-Language
also	O
eliminates	O
the	O
lengthy	O
builds	O
required	O
by	O
HPHPc	B-Language
to	O
run	O
programs	O
,	O
resulting	O
in	O
much	O
simpler	O
development	O
and	O
deployment	O
processes	O
than	O
it	O
was	O
the	O
case	O
with	O
HPHPc	B-Language
.	O
</s>
<s>
Finally	O
,	O
versions	O
of	O
HHVM	B-Language
before	O
4.0	O
have	O
almost	O
complete	O
support	O
for	O
the	O
entire	O
PHP	B-Application
language	I-Application
(	O
as	O
defined	O
by	O
the	O
official	O
implementation	O
of	O
PHP	B-Application
version	O
5.4	O
)	O
,	O
including	O
the	O
support	O
for	O
the	O
create_function( )	O
and	O
eval( )	O
constructs	O
,	O
which	O
was	O
impossible	O
with	O
HPHPc	B-Language
.	O
</s>
<s>
Together	O
with	O
HHVM	B-Language
3.0	O
,	O
Meta	O
also	O
released	O
Hack	B-Language
,	O
a	O
derivative	O
of	O
PHP	B-Application
that	O
allows	O
programmers	O
to	O
use	O
both	O
dynamic	O
typing	O
and	O
static	O
typing	O
(	O
a	O
concept	O
also	O
known	O
as	O
gradual	O
typing	O
)	O
,	O
and	O
allows	O
types	O
to	O
be	O
specified	O
for	O
function	O
arguments	O
,	O
function	O
return	B-Language
values	I-Language
,	O
and	O
class	O
properties	O
.	O
</s>
<s>
However	O
,	O
Hack	B-Language
does	O
not	O
provide	O
complete	O
backward	B-General_Concept
compatibility	I-General_Concept
since	O
it	O
removes	O
several	O
PHP	B-Application
features	O
,	O
such	O
as	O
the	O
goto	B-Application
statement	O
and	O
dynamic	O
variable	O
names	O
.	O
</s>
<s>
In	O
September	O
2017	O
,	O
it	O
was	O
announced	O
that	O
version	O
3.30	O
would	O
be	O
the	O
last	O
version	O
of	O
HHVM	B-Language
to	O
officially	O
support	O
PHP	B-Application
,	O
and	O
that	O
HHVM	B-Language
will	O
only	O
support	O
Hack	B-Language
going	O
forward	O
.	O
</s>
<s>
This	O
was	O
due	O
to	O
differences	O
and	O
incompatibilities	O
in	O
PHP	B-Application
7	O
.	O
</s>
<s>
HHVM	B-Language
4.0	O
,	O
released	O
in	O
February	O
2019	O
,	O
was	O
the	O
first	O
version	O
without	O
support	O
for	O
PHP	B-Application
.	O
</s>
<s>
As	O
a	O
process	O
virtual	B-Architecture
machine	I-Architecture
that	O
provides	O
the	O
execution	O
environment	O
,	O
HHVM	B-Language
has	O
the	O
ability	O
to	O
use	O
live	O
type	O
information	O
to	O
produce	O
more	O
efficient	O
native	B-Language
code	I-Language
,	O
leading	O
to	O
a	O
higher	O
web	O
server	O
throughput	O
and	O
lower	O
latency	O
.	O
</s>
<s>
In	O
Q42012	O
,	O
the	O
execution	O
of	O
com	O
's	O
source	O
code	O
on	O
HHVM	B-Language
achieved	O
performance	O
parity	O
with	O
HPHPc	B-Language
,	O
and	O
in	O
December	O
2013	O
HPHPc	B-Language
was	O
even	O
surpassed	O
by	O
around	O
15%	O
.	O
</s>
