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PHP-FIG PSR Standards Cheat Sheet by DaveChild

A cheat sheet for the PHP standards from the PHP-FIG group.

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PSR-0 - Overview

A fully-­qua­lified namespace and class must have the following structure \<V­endor Name>\­(<N­ame­spa­ce>­\)*­<Class Name>
Each namespace must have a top-level namespace ("Vendor Name").
Each namespace can have as many sub-na­mes­paces as it wishes.
Each namespace separator is converted to a DIRECT­ORY­_SE­PARATOR when loading from the file system.
Each _ character in the CLASS NAME is converted to a DIRECT­ORY­_SE­PAR­ATOR. The _ character has no special meaning in the namespace.
The fully-­qua­lified namespace and class is suffixed with .php when loading from the file system.
Alphabetic characters in vendor names, namesp­aces, and class names may be of any combin­ation of lower case and upper case.

PSR-1 - Overview

Files MUST use only <?php and <?= tags.
Files MUST use only UTF-8 without BOM for PHP code.
Files SHOULD either declare symbols (classes, functions, constants, etc.) or cause side-e­ffects (e.g. generate output, change .ini settings, etc.) but SHOULD NOT do both.
Namespaces and classes MUST follow PSR-0.
Class names MUST be declared in Studly­Caps.
Class constants MUST be declared in all upper case with underscore separa­tors.
Method names MUST be declared in camelCase.

PSR-2 - Overview

Code MUST follow PSR-1.
Code MUST use 4 spaces for indenting, not tabs.
There MUST NOT be a hard limit on line length; the soft limit MUST be 120 charac­ters; lines SHOULD be 80 characters or less.
There MUST be one blank line after the namespace declar­ation, and there MUST be one blank line after the block of use declar­ations.
Opening braces for classes MUST go on the next line, and closing braces MUST go on the next line after the body.
Opening braces for methods MUST go on the next line, and closing braces MUST go on the next line after the body.
Visibility MUST be declared on all properties and methods; abstract and final MUST be declared before the visibi­lity; static MUST be declared after the visibi­lity.
Control structure keywords MUST have one space after them; method and function calls MUST NOT.
Opening braces for control structures MUST go on the same line, and closing braces MUST go on the next line after the body.
Opening parent­heses for control structures MUST NOT have a space after them, and closing parent­heses for control structures MUST NOT have a space before.

PSR-2 - General

Code MUST follow all rules outlined in PSR-1.
All PHP files MUST use the Unix LF (linefeed) line ending.
All PHP files MUST end with a single blank line.
The closing ?> tag MUST be omitted from files containing only PHP.
There MUST NOT be a hard limit on line length.
The soft limit on line length MUST be 120 charac­ters; automated style checkers MUST warn but MUST NOT error at the soft limit.
Lines SHOULD NOT be longer than 80 charac­ters; lines longer than that SHOULD be split into multiple subsequent lines of no more than 80 characters each.
There MUST NOT be trailing whitespace at the end of non-blank lines.
Blank lines MAY be added to improve readab­ility and to indicate related blocks of code.
There MUST NOT be more than one statement per line.
Code MUST use an indent of 4 spaces, and MUST NOT use tabs for indenting.
PHP keywords MUST be in lower case.
The PHP constants true, false, and null MUST be in lower case.

PSR-2 - Namespace and Use Declar­ations

When present, there MUST be one blank line after the namespace declar­ation.
When present, all use declar­ations MUST go after the namespace declar­ation.
There MUST be one use keyword per declar­ation.
There MUST be one blank line after the use block.
 

PSR-2 - Classes, Proper­ties, and Methods

The extends and implements keywords MUST be declared on the same line as the class name.
The opening brace for the class MUST go on its own line; the closing brace for the class MUST go on the next line after the body.
Lists of implements MAY be split across multiple lines, where each subsequent line is indented once. When doing so, the first item in the list MUST be on the next line, and there MUST be only one interface per line.
Visibility MUST be declared on all proper­ties.
The var keyword MUST NOT be used to declare a property.
There MUST NOT be more than one property declared per statement.
Property names SHOULD NOT be prefixed with a single underscore to indicate protected or private visibi­lity.
Visibility MUST be declared on all methods.
Method names SHOULD NOT be prefixed with a single underscore to indicate protected or private visibi­lity.
Method names MUST NOT be declared with a space after the method name.
The opening brace of a method MUST go on its own line, and the closing brace MUST go on the next line following the body.
There MUST NOT be a space after the opening parent­hesis of a method, and there MUST NOT be a space before the closing parent­hesis.
In the argument list, there MUST NOT be a space before each comma, and there MUST be one space after each comma.
Method arguments with default values MUST go at the end of the argument list.
Argument lists MAY be split across multiple lines, where each subsequent line is indented once. When doing so, the first item in the list MUST be on the next line, and there MUST be only one argument per line.
When the argument list is split across multiple lines, the closing parent­hesis and opening brace MUST be placed together on their own line with one space between them.
When present, the abstract and final declar­ations MUST precede the visibility declar­ation.
When present, the static declar­ation MUST come after the visibility declar­ation.
When making a method or function call, there MUST NOT be a space between the method or function name and the opening parent­hesis, there MUST NOT be a space after the opening parent­hesis, and there MUST NOT be a space before the closing parent­hesis.
In the argument list, there MUST NOT be a space before each comma, and there MUST be one space after each comma.

PSR-2 - Control Structures

There MUST be one space after the control structure keyword
There MUST NOT be a space after the opening parent­hesis
There MUST NOT be a space before the closing parent­hesis
There MUST be one space between the closing parent­hesis and the opening brace
The structure body MUST be indented once
The closing brace MUST be on the next line after the body
The body of each structure MUST be enclosed by braces.
The keyword elseif SHOULD be used instead of else if.
The case statement MUST be indented once from switch, and the break keyword (or other termin­ating keyword) MUST be indented at the same level as the case body.
There MUST be a comment such as // no break when fall-t­hrough is intent­ional in a non-empty case body.

PSR-2 - Closures

Closures MUST be declared with a space after the function keyword, and a space before and after the use keyword.
The opening brace MUST go on the same line, and the closing brace MUST go on the next line following the body.
There MUST NOT be a space after the opening parent­hesis of the argument list or variable list, and there MUST NOT be a space before the closing parent­hesis of the argument list or variable list.
In the argument list and variable list, there MUST NOT be a space before each comma, and there MUST be one space after each comma.
Closure arguments with default values MUST go at the end of the argument list.
Argument lists and variable lists MAY be split across multiple lines, where each subsequent line is indented once. When doing so, the first item in the list MUST be on the next line, and there MUST be only one argument or variable per line.
When the ending list (whether or arguments or variables) is split across multiple lines, the closing parent­hesis and opening brace MUST be placed together on their own line with one space between them.
 

PSR-3 - Log Levels (RFC 5424)

debugerror
infocritical
noticealert
warningemergency

PSR-3 - Basics

The Logger­Int­erface exposes eight methods matching log level names (see Log Levels block)
A ninth method, log, accepts a log level as first argument. Calling this method with one of the log level constants MUST have the same result as calling the level-­spe­cific method.
Calling the log method with a level not defined by this specif­ication MUST throw a Psr\Lo­g\I­nva­lid­Arg­ume­ntE­xce­ption if the implem­ent­ation does not know about the level.
Users SHOULD NOT use a custom level without knowing for sure the current implem­ent­ation supports it.

PSR-3 - Message

Every method accepts a string as the message, or an object with a __toSt­ring() method.
The message MAY contain placeh­olders which implem­entors MAY replace with values from the context array.
Placeh­older names MUST correspond to keys in the context array.
Placeh­older names MUST be delimited with a single opening brace { and a single closing brace }. There MUST NOT be any whitespace between the delimiters and the placeh­older name.
Placeh­older names SHOULD be composed only of the characters A-Z, a-z, 0-9, underscore _, and period .. The use of other characters is reserved for future modifi­cations of the placeh­olders specif­ica­tion.
Implem­entors MAY use placeh­olders to implement various escaping strategies and translate logs for display. Users SHOULD NOT pre-escape placeh­older values since they can not know in which context the data will be displayed.

PSR-3 - Context

Every method accepts an array as context data. This is meant to hold any extraneous inform­ation that does not fit well in a string. The array can contain anything.
Implem­entors MUST ensure they treat context data with as much lenience as possible.
A given value in the context MUST NOT throw an exception nor raise any php error, warning or notice.
If an Exception object is passed in the context data, it MUST be in the 'excep­tion' key.
Logging exceptions is a common pattern and this allows implem­entors to extract a stack trace from the exception when the log backend supports it.
Implem­entors MUST still verify that the 'excep­tion' key is actually an Exception before using it as such, as it MAY contain anything.

PSR-3 - Helper Classes and Interfaces

The Psr\Lo­g\A­bst­rac­tLogger class lets you implement the Logger­Int­erface very easily by extending it and implem­enting the generic log method. The other eight methods are forwarding the message and context to it.
The Psr\Lo­g\L­ogg­erTrait only requires you to implement the generic log method. Note that since traits can not implement interf­aces, in this case you still have to implement Logger­Int­erface.
The Psr\Lo­g\N­ull­Logger is provided together with the interface. It MAY be used by users of the interface to provide a fall-back "­black hole" implem­ent­ation if no logger is given to them. However condit­ional logging may be a better approach if context data creation is expensive.
The Psr\Lo­g\L­ogg­erA­war­eIn­terface only contains a setLog­ger­(Lo­gge­rIn­terface $logger) method and can be used by frameworks to auto-wire arbitrary instances with a logger.
The Psr\Lo­g\L­ogg­erA­war­eTrait trait can be used to implement the equivalent interface easily in any class. It gives you access to $this-­>lo­gger.
The Psr\Lo­g\L­ogLevel class holds constants for the eight log levels.

PSR-4 Specif­ication

A fully qualified class name has the following form: \<N­ame­spa­ceN­ame­>(\­<Su­bNa­mes­pac­eNa­mes­>)*­\<C­las­sNa­me>
The fully qualified class name MUST have a top-level namespace name, also known as a "­vendor namesp­ace­".
The fully qualified class name MAY have one or more sub-na­mespace names.
The fully qualified class name MUST have a termin­ating class name.
Unders­cores have no special meaning in any portion of the fully qualified class name.
Alphabetic characters in the fully qualified class name MAY be any combin­ation of lower case and upper case.
All class names MUST be referenced in a case-s­ens­itive fashion.
A contiguous series of one or more leading namespace and sub-na­mespace names, not including the leading namespace separator, in the fully qualified class name (a "­nam­espace prefix­") corres­ponds to at least one "base direct­ory­".
The contiguous sub-na­mespace names after the "­nam­espace prefix­" correspond to a subdir­ectory within a "base direct­ory­", in which the namespace separators represent directory separa­tors. The subdir­ectory name MUST match the case of the sub-na­mespace names.
The termin­ating class name corres­ponds to a file name ending in .php. The file name MUST match the case of the termin­ating class name.
Autoloader implem­ent­ations MUST NOT throw except­ions, MUST NOT raise errors of any level, and SHOULD NOT return a value.
 

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DeeJRoth

Comments

nina nina, 22:35 21 Feb 14

One of the silliest standards for PHP I've ever read.

mike ditka mike ditka, 14:25 10 Apr 14

these standards help autoloading systems integrate your code with such frameworks as laravel or symphony

Aaron Aaron, 21:33 20 Apr 14

Also, if you're going to implement your own autoloader, it's a good idea to check the vendor part of the namespace before you go bothering the file system for class files you know aren't there.

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