A PHP accelerator is a
PHP
PHP is a general-purpose scripting language geared toward web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by The PHP Group ...
extension
Extension, extend or extended may refer to:
Mathematics
Logic or set theory
* Axiom of extensionality
* Extensible cardinal
* Extension (model theory)
* Extension (predicate logic), the set of tuples of values that satisfy the predicate
* E ...
designed to improve the performance of
software
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
applications written in the PHP
programming language
A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language.
The description of a programming ...
.
Operation
Most PHP accelerators work by
caching the compiled
opcode
In computing, an opcode (abbreviated from operation code, also known as instruction machine code, instruction code, instruction syllable, instruction parcel or opstring) is the portion of a machine language instruction that specifies the operat ...
/
bytecode
Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (norma ...
of PHP representation of php files to avoid the overhead of parsing and compiling source code on each request (some or even most of which may never be executed). To further improve performance, the cached code is stored in
shared memory
In computer science, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Shared memory is an efficient means of passing data between progr ...
and directly executed from there, minimizing the amount of slow disk reads and memory copying at runtime.
Practical benefits
PHP accelerators substantially increase the speed of PHP applications. Improvements of web page generation throughput by factors of two to seven have been observed.
The effect on application performance of opcode caching varies widely, depending on factors such as the inherent execution time of the PHP application and the percentage of source code actually executed on a given request, and whether additional optimization steps are performed. While a code
optimizer may even slow down overall performance when used in isolation, it can provide an additional performance boost when coupled with a bytecode cache, as the optimization effort is performed just once.
See also
*
List of PHP accelerators
This is a list of PHP accelerators.
Alternative PHP Cache (APC)
Alternative PHP Cache is a free and open (PHP license) framework that caches the output of the PHP bytecode compiler in shared memory, thus reducing parsing and disk I/O overhead ...
References
External links
Alternative PHP Cache a widely used opcode cache.
Free proxy servers
PHP software
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