Summary of PHP Features by versions

php-features-by-versions.md

PHP 7

• Scalar type declarations
• Return type declarations
• Null coalescing operator
• Spaceship operator
• Constant arrays using define()
• Anonymous classes
• Unicode codepoint escape syntax
• Closure::call()
• Filtered unserialize()
• IntlChar
• Expectations
• Group use declarations
• Generator Return Expressions
• Generator delegation
• Integer division with intdiv()
• Session options
• preg_replace_callback_array()
• CSPRNG Functions
• list() can always unpack objects implementing ArrayAccess

PHP 5.6

• Constant expressions
• Variadic functions via ...
• Argument unpacking via ...
• Exponentiation via **
• use function and use const
• phpdbg
• Default character encoding
• php://input is reusable
• Large file uploads
• GMP supports operator overloading
• hash_equals() for timing attack safe string comparison
• __debugInfo()
• gost-crypto hash algorithm
• SSL/TLS improvements
• pgsql async support

PHP 5.5

• Generators added
• finally keyword added
• New password hashing API
• foreach now supports list()
• empty() supports arbitrary expressions
• array and string literal dereferencing
• Class name resolution via ::class
• OPcache extension added
• foreach now supports non-scalar keys
• Apache 2.4 handler supported on Windows
• Improvements to GD

PHP 5.4

• Support for traits has been added.
• Short array syntax has been added, e.g. $a = [1, 2, 3, 4]; or $a = ['one' => 1, 'two' => 2, 'three' => 3, 'four' => 4];.
• Function array dereferencing has been added, e.g. foo()[0].
• Closures now support $this.
• Class member access on instantiation has been added, e.g. (new Foo)->bar().
• Class::{expr}() syntax is now supported.
• Binary number format has been added, e.g. 0b001001101.
• Improved parse error messages and improved incompatible arguments warnings.
• The session extension can now track the upload progress of files.
• Built-in development web server in CLI mode.

PHP 5.3

• Support for namespaces has been added.
• Support for Late Static Bindings has been added.
• Support for jump labels (limited goto) has been added.
• Support for native Closures (Lambda/Anonymous functions) has been added.
• There are two new magic methods, __callStatic() and __invoke().
• Nowdoc syntax is now supported, similar to Heredoc syntax, but with single quotes.
• It is now possible to use Heredocs to initialize static variables and class properties/constants.
• Heredocs may now be declared using double quotes, complementing the Nowdoc syntax.
• Constants can now be declared outside a class using the const keyword.
• The ternary operator now has a shorthand form: ?:.
• The HTTP stream wrapper now considers all status codes from 200 to 399 to be successful.
• Dynamic access to static methods is now possible
• Exceptions can now be nested
• A garbage collector for circular references has been added, and is enabled by default.
• The mail() function now supports logging of sent email via the mail.log configuration directive. (Note: This only applies to email sent through this function.)