Coding Standard PHP

8/13/2019 Coding Standard PHP

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Coding StandardFor PHPRevision o!"."Created on! #$%ov%#&"'

(ast )odi*ied on! "&%+ul%#&"'
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Table of Contents

" ,uthorisation...............................................................................................................................-

# Revision History..........................................................................................................................

' PHP File Formatting.....................................................................................................................

- Class ames.............................................................................................................................../

)ethod and Function ames.......................................................................................................0

/ Class (i1rary ames...................................................................................................................2

0 )ethod ames............................................................................................................................2

2 Class ,ttri1ute ames.................................................................................................................$

$ )ethod ,rgument ames...........................................................................................................$

"& 3aria1le ames.........................................................................................................................$

"" ,rray 4lement........................................................................................................................."&

"# Single or Dou1le 5uotes..........................................................................................................""

"' Re*erence 3aria1les and Functions Returning Re*erences......................................................""

"- 6lo1al 3aria1les......................................................................................................................""

" De*ine ames 7 6lo1al Constants............................................................................................"#

"/ Static 3aria1les......................................................................................................................."#

"0 Function ames......................................................................................................................"#

"2 4rror Return Chec8 Policy......................................................................................................."#

"$ 9races :; Policy......................................................................................................................"'

#& with ?ey @ords and Functions Policy......................................................................."

## Do ot do Real @or8 in A1Bect Constructors..........................................................................."/

#'


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! Revision "istory

# P"P $ile $ormatting

%eneral

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Coding Standard


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For *iles that contain only PHP codeG the closing tag =IJ> is never permitted.


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,ethod and $un(tion Names

sually every method and *unction per*orms an actionG so the name should ma8e clear

what it does! Chec8For4rrors=> instead o* 4rrorChec8=>G DumpDataToFile=> instead o*

DataFile=>. This will also ma8e *unctions and data o1Bects more distinguisha1le.

Su**iEes are sometimes use*ul!

o Max% to mean the maEimum value something can have.

o Cnt% the current count o* a running count varia1le.

o Key% 8ey value.

For eEample! Retry)aE to mean the maEimum num1er o* retriesG RetryCnt to mean the

current retry count.

Pre*iEes are sometimes use*ul!o Is% to as8 a question a1out something. @henever someone sees Isthey will 8now

itKs a question.

o Get% get a value.

o Set% set a value.

For eEample!


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se upper case letters as word separatorsG lower case *or the rest o* a word

First character in a name is upper case

o under1ars =KNK>

3ustifi(ation

A* all the di**erent naming strategies many people *ound this one the 1est compromise.

Eample

class ameAneTwo

class ame

4 Class .ibrary Names

ow that name spaces are 1ecoming more widely implementedG name spaces should 1e

used to prevent class name con*licts among li1raries *rom di**erent vendors and groups.

@hen not using name spacesG itKs common to prevent class name clashes 1y pre*iEing

class names with a unique string. Two characters is su**icientG 1ut a longer length is *ine.

Eample

+ohn +ohnsonKs complete data structure li1rary could useJJas a pre*iEG so classes would 1e!

class +B(in8(ist

:

;

5 ,ethod Names

se the same rule as *or class names.

3ustifi(ation

A* all the di**erent naming strategies many people *ound this one the 1est compromise.

Eample

class ameAneTwo

:

*unction Do :;O

*unction Handle4rror=> :;O

;

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Coding Standard


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6 Class Attribute Names

Class mem1er attri1ute names should 1e prepended with the character KmK.

,*ter the KmK use the same rules as *or class names.

KmK always precedes other name modi*iers li8e KrK *or re*erence.

3ustifi(ation

Prepending KmK prevents any con*lict with method names. A*ten your methods and

attri1ute names will 1e similarG especially *or accessors.

Eample

class ameAneTwo

:

*unction 3ar,1c=> :;O

*unction 4rrorum1er=> :;O

var m3ar,1cO

var m4rrorum1erO

var mrameO

;

7 ,ethod Argument Names

The *irst character should 1e lower case.

,ll word 1eginnings a*ter the *irst letter should 1e upper case as with class names.

3ustifi(ation

ou can always tell which varia1les are passed in varia1les.

Eample

class ameAneTwo

:

*unction Startour4ngines=Qsome4ngineG Qanother4ngine> :

this%JmSome4ngine some4ngineO

this%Jm,nother4ngine another4ngineO

;

var mSome4ngineO

var m,nother4ngineO

;

18 9ariable Names

use all lower case letters

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Coding Standard


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use KNK as the word separator.

3ustifi(ation

@ith this approach the scope o* the varia1le is clear in the code.

ow all varia1les loo8 di**erent and are identi*ia1le in the code.

Eample

*unction Handle4rror=errorum1er>

:

error new As4rrorO

timeNo*Nerror error%J6etTimeA*4rror=>O

errorNprocessor error%J6et4rrorProcessor=>O

;

11 Array Element

,rray element names *ollow the same rules as a varia1le.

use KNK as the word separator.

donKt use K%K as the word separator

3ustifi(ation

i* K%K is used as a word separator it will generate warnings used with magic quotes.

EamplemyarrK*ooN1arK KHelloKO

print myarr*ooN1ar worldO 77 will output! Hello world

myarrK*oo%1arK KHelloKO

print myarr*oo%1ar worldO 77 warning message

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Coding Standard


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1! Single or ouble :uotes

,ccess an arrayKs elements with single or dou1le quotes.

DonKt use quotes within magic quotes

3ustifi(ation

Some PHP con*igurations will output warnings i* arrays are used without quotes eEcept

when used within magic quotes

Eample

myarrK*ooN1arK KHelloKO

elementNname K*ooN1arKO

print myarr*ooN1ar worldO 77 will output! Hello world

print myarrelementNname worldO 77 will output! Hello world

print myarrKelementNnameK worldO 77 parse error

print myarrelementNname worldO 77 parse error

1# Referen(e 9ariables and $un(tions Returning Referen(es

Re*erences should 1e prepended with KrK.

3ustifi(ation

The di**erence 1etween varia1le types is clari*ied.

:;O

*unction QrStatus=> :;O

;

10 %lobal 9ariables

6lo1al varia1les should 1e prepended with a KgK.

3ustifi(ation


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1 efine Names ; %lobal Constants

6lo1al constants should 1e all caps with KNK separators.

3ustifi(ation

O

14 Stati( 9ariables

Static varia1les may 1e prepended with KsK.

3ustifi(ation

:

static msStatus &O

;

15 $un(tion Names

For PHP *unctions use the C 6 convention o* all lower case letters with KNK as the word

delimiter.

3ustifi(ation

:

;

16 Error Return Che(/ Poli(y

Chec8 every system call *or an error returnG unless you 8now you wish to ignore errors.


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17 while =condition>

: :

... ...

; ;

Traditional niE policy o* placing the initial 1race on the same line as the 8eyword and

the trailing 1race inline on its own line with the 8eyword!

i* =condition> : while =condition> :

... ...

; ;

3ustifi(ation

,nother religious issue o* great de1ate solved 1y compromise. 4ither *orm is accepta1leG

many peopleG howeverG *ind the *irst *orm more pleasant. @hy is the topic o* many

psychological studies.

There are more reasons than psychological *or pre*erring the *irst style. that supports 1race matchingG the *irst is a much 1etter style. @hyI

(etKs say you have a large 1loc8 o* code and want to 8now where the 1loc8 ends. ou

move to the *irst 1race hit a 8ey and the editor *inds the matching 1race. 4Eample!

i* =veryNlongNcondition QQ secondNveryNlongNcondition>

:

...

;

else i* =...> :

...

;

To move *rom 1loc8 to 1loc8 you Bust need to use cursor down and your 1race matching

8ey. o need to move to the end o* the line to match a 1race then Ber8 1ac8 and *orth.

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Coding Standard


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!8 +ndentation;Tabs;Spa(e Poli(y

:

while =more input>

:

;

;

;

;

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Coding Standard


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!1 Parens ()with =ey >ords and $un(tions Poli(y

Do not put parens neEt to 8eywords. Put a space 1etween.

Do put parens neEt to *unction names.

Do not use parens in return statements when itKs not necessary.

3ustifi(ation

?eywords are not *unctions. 9y putting parens neEt to 8eywords 8eywords and *unction

names are made to loo8 ali8e.

Eample

i* =condition>

:

;

while =condition>

:

;

strcmp=sG s">O

return "O

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Coding Standard


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!! o Not do Real >or/ in ?b@e(t Constru(tors

Do not do any real wor8 in an o1BectKs constructor. method *or an o1Bect which completes construction. Apen=> should 1e

called a*ter o1Bect instantiation.

3ustifi(ation

Constructors canKt return an error.

Eample

class Device

:

*unction Device=> : 7U initialiMe and other stu** U7 ; *unction Apen=> : return F, eEit=">O

,a/e $un(tions Reentrant

Functions should not 8eep static varia1les that prevent a *unction *rom 1eing reentrant.

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Coding Standard


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!# +f Then Else $ormatting

.ayout

77 Comment :

;

else i* =condition> 77 Comment

:

;

else 77 Comment

:

;

...

Ane reason is that i* you leave out one o* the signsG the parser will *ind the error *or you. ,

second reason is that it puts the value you are loo8ing *or right up *ront where you can *ind

it instead o* 1uried at the end o* your eEpression.


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!0 switch$ormatting

Falling through a case statement into the neEt case statement shall 1e permitted as long

as a comment is included.

The defaultcase should always 1e present and trigger an error i* it should not 1e

reachedG yet is reached.

:

case "!

...

77 F,(( THRA6H

case #!

:

v getNwee8Nnum1er=>O

...

;

1rea8O

de*ault! ;

2se of continuebreakand B

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Coding Standard


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! Continue and 1rea8O

;

ote! , lot o* code is necessary in order that the pro1lem cannot 1e caught easily 1y

the programmer.

From the a1ove eEampleG a *urther rule may 1e given! )iEing continue with 1rea8 in the

same loop is a sure way to disaster.

B

The trou1le is people usually try and stu** too much code in 1etween the ?and :. Here are a

couple o* clarity rules to *ollow!

Put the condition in parens so as to set it o** *rom other code


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Eample

=condition> I *unct"=> ! *unc#=>O

or

=condition>

I long statement ! another long statementO

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Coding Standard


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!4 Alignment of e(laration .

!5 o(ument Null Statements,lways document a null 1ody *or a *or or while statement so that it is clear that the null 1ody

is intentional and not missing code.

while =destVV srcVV>

O 77 3A


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!6 o Not efault +f Test to Non-Dero

Do not de*ault the test *or non%MeroG i.e.

i* =F,>

is 1etter than

i* =*=>>

even though F,O instead test *or inequality

with & =F,(S4G AG etc.>. )ost *unctions are guaranteed to return & i* *alseG 1ut only non%Mero

i* true. ThusG

i* =TR4 *unc=>> : ...

must 1e written

i* =F,(S4 L *unc=>> : ...

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Coding Standard


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#8 2sually Avoid Embedded Assignments

There is a time and a place *or em1edded assignment statements. >>

:

process the character

;

The VV and %% operators count as assignment statements. SoG *or many purposesG do

*unctions with side e**ects. sing em1edded assignment statements to improve run%time

per*ormance is also possi1le. HoweverG one should consider the tradeo** 1etween increased

speed and decreased maintaina1ility that results when em1edded assignments are used in

arti*icial places. For eEampleG

a 1 V cO

d a V rO

should not 1e replaced 1y

d =a 1 V c> V rO

even though the latter may save one cycle. or/ of ?thers

Reuse across proBects is almost impossi1le without a common *ramewor8 in place. A1Bects

con*orm to the services availa1le to them. Di**erent proBects have di**erent service

environments ma8ing o1Bect reuse di**icult.

Developing a common *ramewor8 ta8es a lot o* up *ront design e**ort. @hen this e**ort is not

madeG *or whatever reasonsG there are several techniques one can use to encourage reuse!

onKt be Afraid of Small .ibraries

Ane common enemy o* reuse is people not ma8ing li1raries out o* their code. , reusa1le

class may 1e hiding in a program directory and will never have the thrill o* 1eing shared

1ecause the programmer wonKt *actor the class or classes into a li1rary.

Ane reason *or this is 1ecause people donKt li8e ma8ing small li1raries. ThereKs something

a1out small li1raries that doesnKt *eel right. 6et over it. The computer doesnKt care how

many li1raries you have.

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Coding Standard


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Comment .ayout

4ach part o* the proBect has a speci*ic comment layout.

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Coding Standard


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,a/e %ot(has Epli(it

4Eplicitly comment varia1les changed out o* the normal control *low or other code li8ely to

1rea8 during maintenance. 4m1edded 8eywords are used to point out issues and potential

pro1lems. Consider a ro1ot will parse your comments loo8ing *or 8eywordsG stripping them

outG and ma8ing a report so people can ma8e a special e**ort where needed.

%ot(ha =eywords

T?? topi(

)eans thereKs more to do hereG donKt *orget.


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77 !?(D64! tmh $/&2"&! possi1le unsa*e type cast

77 @e need a cast here to recover the derived type.


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## ire(tory o(umentation

4very directory should have a R4,D)4 *ile that covers!

the purpose o* the directory and what it contains

a one line comment on each *ile. , comment can usually 1e eEtracted *rom the ,)4

attri1ute o* the *ile header.

cover 1uild and install directions

direct people to related resources!

o directories o* source

o online documentation

o paper documentation

o design documentation

anything else that might help someone

Consider a new person coming in / months a*ter every original person on a proBect has gone.

That lone scared eEplorer should 1e a1le to piece together a picture o* the whole proBect 1y

traversing a source directory tree and reading R4,D)4 *ilesG )a8e*ilesG and source *ile

headers.

?pen;Closed Prin(iple

The Apen7Closed principle states a class must 1e open and closed where!

open means a class has the a1ility to 1e eEtended.

closed means a class is closed *or modi*ications other than eEtension. The idea is once a

class has 1een approved *or use having gone through code reviewsG unit testsG and other

quali*ying proceduresG you donKt want to change the class very muchG Bust eEtend it.

The Apen7Closed principle is a pitch *or sta1ility. , system is eEtended 1y adding new code

not 1y changing already wor8ing code. Programmers o*ten donKt *eel com*orta1le changing

old code 1ecause it wor8sL This principle Bust gives you an academic sounding Busti*ication *or

your *ears !%>


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#0 Server (onfiguration

This section contains some guidelines *or PHP7,pache con*iguration.

"TTPO9ARS

HTTPNUN3,RS are either ena1led or disa1led. @hen ena1led all varia1les must 1e accessed

through HTTPNUN3,RS8ey. @hen disa1led all varia1les can 1e accessed 1y the 8ey name.

use HTTPNUN3,RS when accessing varia1les.

use ena1led HTTPNUN3,RS in PHP con*iguration.

3ustifi(ation

HTTPNUN3,RS is availa1le in any con*iguration.

HTTPNUN3,RS will not con*lict with eEsisting varia1les.

sers canKt change varia1les 1y passing values.

# P"P $ile Etensions

There is lots o* di**erent eEtension variants on PHP *iles =.htmlG .phpG .php'G .php-G .phtmlG

.incG .class...>.

,lways use the eEtension .php.

,lways use the eEtension .php *or your class and *unction li1raries.

3ustifi(ation

The use o* .php ma8es it possi1le to ena1le caching on other *iles than .php.

The use o* .inc or .class can 1e a security pro1lem. An most servers these eEtensions

arenKt set to 1e run 1y a parser. .

Do not rely on automatic 1eauti*iers. The main person who 1ene*its *rom good program

style is the programmer him7hersel*G and especially in the early design o* handwritten

algorithms or pseudo%code. ,utomatic 1eauti*iers can only 1e applied to completeG

syntactically correct programs and hence are not availa1le when the need *or attention to

white space and indentation is greatest. Programmers can do a 1etter Bo1 o* ma8ing clear

the complete visual layout o* a *unction or *ileG with the normal attention to detail o* a

care*ul programmer =in other wordsG some o* the visual layout is dictated 1y intent rather

than syntaE and 1eauti*iers cannot read minds>. Sloppy programmers should learn to 1e

care*ul programmers instead o* relying on a 1eauti*ier to ma8e their code reada1le.

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FinallyG since 1eauti*iers are non%trivial programs that must parse the sourceG a

sophisticated 1eauti*ier is not worth the 1ene*its gained 1y such a program. 9eauti*iers

are 1est *or gross *ormatting o* machine%generated code.

,ccidental omission o* the second ZZKK o* the logical compare is a pro1lem. The *ollowing

is con*using and prone to error. i* =a1ool 11ool> : ... ;

Does the programmer really mean assignment hereI A*ten yesG 1ut usually no. The

solution is to Bust not do itG an inverse i8e philosophy. : ... ;

2se if )8* to Comment ?ut Code 1loc8!

*unction eEample=>

:

great loo8ing code

i* =&> :

lots o* code

;

more code

;

ou canKt use ;OO;style comments 1ecause comments canKt contain comments and surely alarge 1loc8 o* your code will contain a commentG wonKt itI

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Coding Standard


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#4 ifferent A((essor Styles

+mplementing A((essors

There are two maBor idioms *or creating accessors.

%et;Set

class [

:

*unction 6et,ge=> : return this%Jm,geO ;

*unction Set,ge=age> : this%Jm,ge ageO ;

var m,geO

;O

6et7Set is ugly. 6et and Set are strewn throughout the code cluttering it up.

9ut one 1ene*it is when used with messages the set method can transparently trans*orm

*rom native machine representations to networ8 1yte order.

Attributes as ?b@e(ts

class [

:

*unction ,ge=> : return this%Jm,geO ;

*unction ame=> : return this%JmameO ;

var m,geO

var mameO

;

E new [O

77 4Eample "

age E%J,ge=>O

rNage QE%J,ge=>O 77 Re*erence

77 4Eample #

name E%Jame=>O

rNname QE%Jame=>O 77 Re*erence

,ttri1utes as A1Bects is clean *rom a name perspective. @hen possi1le use this approach to

attri1ute access.

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Coding Standard


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#5 .ayering

(ayering is the primary technique *or reducing compleEity in a system. , system should 1e

divided into layers. (ayers should communicate 1etween adBacent layers using well de*ined

inter*aces. @hen a layer uses a non%adBacent layer then a layering violation has occurred.

, layering violation simply means we have dependency 1etween layers that is not controlled

1y a well de*ined inter*ace. @hen one o* the layers changes code could 1rea8. @e donKt

want code to 1rea8 so we want layers to wor8 only with other adBacent layers.

Sometimes we need to Bump layers *or per*ormance reasons. This is *ineG 1ut we should

8now we are doing it and document appropriately.

#6 Code Reviews


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#7 Create a Sour(e Code Control System Early and Not ?ften

, common 1uild system and source code control system should 1e put in place as early as

possi1le in a proBectKs li*ecycleG pre*era1ly 1e*ore anyone starts coding. Source code control

is the structural glue 1inding a proBect together.


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Create a


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*ormats will cause con*licts with persistent stores or remote message sending then say so.


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01 No ,agi( Numbers

, magic num1er is a 1are%na8ed num1er used in source code.


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0! Thin vs' $at Class +nterfa(es

How many methods should an o1Bect haveI The right answer o* course is Bust the right

amountG weKll call this the 6oldiloc8s level. 9ut what is the 6oldiloc8s levelI

The two eEtremes are thinclasses versus thi(/classes. Thin classes are minimalist classes.

Thin classes have as *ew methods as possi1le. The eEpectation is users will derive their own

class *rom the thin class adding any needed methods.

@hile thin classes may seem clean they really arenKt. ou canKt do much with a thin class.

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