PHP 5.5.0 released!

PHP 5.5 has been released! Quite exciting stuff, and pretty great to see the pace of new releases. Props to the dev team!

Hopefully distros pick this version up quickly as well, so we can start making use of these fancy new features.

The highlights:

Generators

Generators provide an extremely easy way to create iterators. They introduce a new yield keyword, which kinda works like return, but different:

<?php

function daysOfTheYear() {

    $year = date('Y');
    $current = new DateTimeImmutable($year . '-01-01');

    do {

        yield $current;
        $current = $current->modify('+1 day');

    } while ($current->format('Y') === $year);

}

foreach(daysOfTheYear() as $dt) {

    // ...

}

?>

The benefit of this new syntax, is that you can now let these new generators act as if they returned an array, loop through them as usual, but the actual array doesn't need to be in memory in advance.

More information on php.net.

Immutable DateTime object

In my previous example I used DateTimeImmutable. In my job I deal a lot with dates and times. DateTime is therefore my tool of choice.

One mild annoyance, is that whenever DateTime objects are passed as arguments to any method, and you intend to do calculations based on them, you really want to make sure that you're not modifying the original.

<?php

function printUTCTime(DateTime $dt) {

    $dt->setTimeZone(new DateTimeZone('UTC'));
    echo $dt->format(DateTime::ATOM);

}

// Created in a local timezone
$dt = new DateTime('now');
printUTCTime($dt);

// Now $dt is suddenly in UTC.

?>

Because my function name was called printUTCTime, as a consumer of this function it would go against my expectations that the object was also modified. I'd expect it to just echo.

So, as a library developer I should first always clone any DateTime I get, before doing anything with them.

DateTimeImmutable is a new object, similar to DateTime. The difference is that it's, well, immutable. This means that after the object has been created, it's guarenteed to never change.

Methods like modify, setTimeZone and setTimeStamp never alter the object, but always return a modified copy.

Now, if we can also solve the following API usability feature, I'd be totally happy:

<?php

$dt = new DateTime('2013-06-20 16:00:00', new DateTimeZone('Europe/London'));
$dt->setTimeZone(new DateTimeZone('Europe/London'));

?>

The previous example is, as far as I know, the only way to create a DateTime object in a specific timezone. The first timezone is needed to tell DateTime what the reference timezone is, the latter to actually change it into that timezone.

Anyway, as soon as my libraries require PHP 5.5, I'll be changing all my DateTime objects to DateTimeImmutable.

Lists in foreach

This adds some syntax sugar for some foreach loops. I quite like it:

<?php

$users = [
    ['Foo', 'Bar'],
    ['Baz', 'Qux'],
];

foreach ($users as list($firstName, $lastName)) {
    echo "First name: $firstName, last name: $lastName. ";
}

?>

Example was directly taken from the wiki.

Finally keyword

Finally, the finally keyword is also implemented into the language. (sorry, had to do it).

finally can be added to try..catch block, and guarantees that regardless of what happened within that block, finallywill always be executed.

<?php

try {

  echo "1";
  throw new Exception();

} catch (Exception $e) {

  // Handle exception
  echo "2";

} finally {

  echo "3";

}

?>

The preceeding example will output 123. The benefit of finally, is that it's contents will also be executed if the exception was not caught. If you need any guaranteed cleanup, finally is your tool.

Class name resolution

I write a lot of code that maps data structures to classes. An example of this can be seen in my vobject project.

As you can see there, that's a huge list with a ton of repetition. The reason for this lies in the fact that when you specify a classname as a string, you cannot use namespace resolution.

Simpler example:

<?php

$class = 'Sabre\\VObject\\Property\\ICalendar\\CalAddress';
$obj = new $class();

?>

Well, starting from PHP 5.5, I can use a syntax like this instead:

<?php

use Sabre\VObject\Property\ICalendar;

$class = ICalendar\CalAddress::class;
$obj = new $class();

?>

Much cleaner, and prettier! Especially if you have a hundred of those in one file.

Opcode cache is now integrated and enabled by default in PHP

For years we had to manually install APC as a first step after installing PHP. It seemed silly that 'being fast' was not considered an essential language feature.

Now it is, and it wasn't APC that made it into core, but rather an alternative from Zend.

Some more info can be found on the wiki.

Constant dereferencing

This is really just a fancy word for being able to do the following:

<?php

echo "Hello"[1]; // output 'e'
echo [1,2,3,4][3]; // output '4'

?>

Why is this cool? Not sure; I'm still trying to figure out when I'll use this, but It's great to see that the PHP engine is getting more consistent.

To conclude