PHP 7.4 Released

Weedpacket · Nov 30, 2019

Release Announcement
This is a new-feature release, where backward incompatibilities are mainly restricted to not being quite as carefree about programmer silliness (trying to address an array element of an integer will generate a notice). The embedded MySQLi server has been removed (remember the embedded MySQLi server? Neither did anyone else. Which is why no-one used it. No wonder it went so long without it actually working.)

More fun to talk about are the new features.

a new FFI extension that provides a runtime mapping directly between PHP code and external shared/dynamic libraries. This one's still experimental, but it's nice that PHP is now able to talk to other programs this way.
Object properties can have types assigned to them:
```
protected int $someinteger;
```
better support in type declarations; some (co|contra)variance support in declaring return/parameter types of methods in subclasses.
```
   interface Base {}
   interface Derived extends Base {}
   

   class ParentClass { public function doStuff(): Base{/* */}}
   class ChildClass extends ParentClass { public function doStuff(): Derived{/* */}}
   
```
Previously, ChildClass::doStuff() would have had to have been declared as returning an instance of Base because that's what its parent class said, even though it would only ever return Derived; that loss of discrimination limited how much could be said later on if you wanted to restrict an input type to Derived.
a ??= operator that serves to set a variable to a given value only if the variable doesn't have a value already:
```
$input['field'] ??= $defaultField;
```
instead of
```
if(!isset($input['field'])) $input['field'] = $defaultField;
```
As well as being tidier and more quickly read, the new syntax means identifying the variable only has to be done once.

the ... can be used inside array literals to interpolate other arrays:

$inner = [1, 2, 3, 4];
$more = ["foo", "bar", ...$inner, "baz"];
echo '[' . join(", ", $more) . ']'; // [foo, bar, 1, 2, 3, 4, baz]

numeric literals can have embedded _ just to make them easier to read in code (especially helpful when writing numbers in binary)
```
$mask = 0b0000_1010_0000;
```
instead of
```
$mask = 0b000010100000;
```
or
```
$mask = 0xa0;
```
a less-quirky method for whitelisting tags in strip_tags;
```
strip_tags($input, ['a', 'b']);
```
instead of
```
strip_tags($input, '<a><b>');
```

the new fn keyword has been added to allow a more streamlined syntax for single-statement inline functions;

$maxlength = 76;
$truncated_lines = array_map(fn($line) => substr($line, 0, $maxlength), $lines);

instead of

$maxlength = 76;
$truncated_lines = array_map(function($line)use($maxlength) {
    return substr($line, 0, $maxlength);
}, $lines);

There is a lot more than just these, of course. The release announcement is at the top of this post; for the manual's take, see Migrating from PHP 7.3.x to PHP 7.4.x.