<s>
The	O
PHP	B-Protocol
serialization	I-Protocol
format	I-Protocol
is	O
the	O
serialization	B-Application
format	O
used	O
by	O
the	O
PHP	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
The	O
format	O
can	O
serialize	B-Application
PHP	B-Application
's	O
primitive	O
and	O
compound	O
types	O
,	O
and	O
also	O
properly	O
serializes	B-Application
references	O
.	O
</s>
<s>
The	O
format	O
was	O
first	O
introduced	O
in	O
PHP	B-Application
4	O
.	O
</s>
<s>
In	O
addition	O
to	O
PHP	B-Application
,	O
the	O
format	O
is	O
also	O
used	O
by	O
some	O
third-party	O
applications	O
that	O
are	O
often	O
integrated	O
with	O
PHP	B-Application
applications	O
,	O
for	O
example	O
by	O
Lucene/Solr	B-Language
.	O
</s>
