What is PSR? PSR is a standard established by PHP-FIG(PHP Framework Interop Group).
PSR consists of several standards such as PSR-1, PSR-2 and PSR-4.
PSR-0 and PSR-4 are coding standards for PHP’s autoloaders, PSR-1 and PSR-2 are basic coding standards.
PHP code MUST use only UTF-8 without BOM(Byte Order Mark).
PSR-1 Basic Coding Standard, defines basic parts of PHP coding Only <?php ?> or <?= ?> are allowed for PHP tags Files must be in UTF-8 without BOM(Byte Order Mark) Namespaces and class names must follow the standards in PSR-0 and PSR-4 Class names must be defined in UpperCamelCase Class variables must be defined in UPPER_SNAKE_CASE Method names must be defined in camelCase // defining normal properties in camelCase // defining static properties in UpperCamelCase // Class constants MUST be declared in all upper case with underscore separators class Something { public $normalPropterty; public static $StaticProperty; const VERSION = '1.0'; const DATE_APPROVED = '2000-12-01'; } PSR-2 Coding style Guide, an extension of PSR-1 You must follow PSR-1 coding standards 4 spaces must be used for indents. Using tabs is not allowed There is no limit to line length, but it should be under 120 characters, and best if under 80 You must put a newline before curly braces for classes and methods Methods and properties must be defined with abstract/final first, followed with public/protected, and finally static. You must not put a newline before curly braces in conditional statements You must not put any spaces before ( and ) in conditional statements PSR-12: Extended Coding Style, is now recommended for PSR-2. .php files must use Unix LF(linefeed) line \n ending only. .php files must end with a non-blank line. closing ?> tag must be omitted from .php files containing only php. Compound namespaces with a depth of more than two MUST NOT be used.
namespace SubnamespaceOne\Anothernamespace\ClassA; <?php /** * This file contains an example of coding styles. */ declare(strict_types=1); // MUST be one blank line after the namespace declaration namespace Vendor\Package; // MUST be one blank line after the block of use declarations. use Vendor\Package\{ClassA as A, ClassB, ClassC as C}; use Vendor\Package\SomeNamespace\ClassD as D; use function Vendor\Package\{functionA, functionB, functionC}; use const Vendor\Package\{ConstantA, ConstantB, ConstantC}; use Vendor\Package\FirstTrait; // Opening braces for classes MUST go on the next line, and closing braces MUST go on the next line after the body. class Foo extends Bar implements FooInterface { // use keyword used inside the classes to implement traits MUST be declared on the next line after the opening brace. use FirstTrait; // Opening braces for methods MUST go on the next line, and closing braces MUST go on the next line after the body. public function sampleFunction(int $a, int $b = null): array { if ($a === $b) { bar(); } elseif ($a > $b) { $foo->bar($arg1); } else { BazClass::bar($arg2, $arg3); } } // abstract and final MUST be declared before the visibility; // static MUST be declared after the visibility. final public static function bar() { // method body } } Reference PSR-1 PSR-2 PSR-12 5 PHP coding statands Code Sytle Guide