PHP-FIG PSR Standards Cheat Sheet by DaveChild

A fully-­qua­lified namespace and class must have the following structure \<V­endor Name>­\(<N­ame­spa­ce>­\)*­<Class Name>

Each namespace can have as many sub-na­mes­paces as it wishes.

Each _ character in the CLASS NAME is converted to a DIRECT­ORY­_SE­PAR­ATOR. The _ character has no special meaning in the namespace.

Alphabetic characters in vendor names, namesp­aces, and class names may be of any combin­ation of lower case and upper case.

Files MUST use only <?php and <?= tags.

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.

Class names MUST be declared in Studly­Caps.

Method names MUST be declared in camelCase.

Code MUST follow PSR-1.

There MUST NOT be a hard limit on line length; the soft limit MUST be 120 charac­ters; lines SHOULD be 80 characters or less.

Opening braces for classes 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.

Opening braces for control structures MUST go on the same line, and closing braces MUST go on the next line after the body.

Code MUST follow all rules outlined in PSR-1.

All PHP files MUST end with a single blank line.

There MUST NOT be a hard limit on line length.

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.

Blank lines MAY be added to improve readab­ility and to indicate related blocks of code.

Code MUST use an indent of 4 spaces, and MUST NOT use tabs for indenting.

The PHP constants true, false, and null MUST be in lower case.

When present, there MUST be one blank line after the namespace declar­ation.

There MUST be one use keyword per declar­ation.

The extends and implements keywords MUST be declared on the same line as the class name.

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.

The var keyword MUST NOT be used to declare a property.

Property names SHOULD NOT be prefixed with a single underscore to indicate protected or private visibi­lity.

Method names SHOULD NOT be prefixed with a single underscore to indicate protected or private visibi­lity.

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.

In the argument list, there MUST NOT be a space before each comma, and there MUST be one space after each comma.

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 present, the abstract and final declar­ations MUST precede 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.

There MUST be one space after the control structure keyword

There MUST NOT be a space before the closing parent­hesis

The structure body MUST be indented once

The body of each structure MUST be enclosed by braces.

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.

Closures MUST be declared with a space after the function keyword, and a space before and after the use keyword.

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.

Closure arguments with default values MUST go at the end of the argument list.

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.

The Logger­Int­erface exposes eight methods matching log level names (see Log Levels block)

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.

Every method accepts a string as the message, or an object with a __toSt­ring() method.

Placeh­older names MUST correspond to keys in the context array.

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.

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.

A given value in the context MUST NOT throw an exception nor raise any php error, warning or notice.

Logging exceptions is a common pattern and this allows implem­entors to extract a stack trace from the exception when the log backend supports it.

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\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\L­ogg­erA­war­eTrait trait can be used to implement the equivalent interface easily in any class. It gives you access to $this-­>lo­gger.

A fully qualified class name has the following form: \<N­ame­spa­ceN­ame­>(­\<Su­bNa­mes­pac­eNa­mes­>)*­\<C­las­sNa­me>

The fully qualified class name MAY have one or more sub-na­mespace names.

Unders­cores have no special meaning in any portion of the fully qualified class name.

All class names MUST be referenced in a case-s­ens­itive fashion.

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.

Autoloader implem­ent­ations MUST NOT throw except­ions, MUST NOT raise errors of any level, and SHOULD NOT return a value.