What’s New in PHP 5.5
PHP array of the values between the
$start and
$end arguments. We can use
range() as follows:
<?php foreach (range(0, 1000000) as $number) { echo $number; }
The problem in this example is that the array returned by
range() will occupy a lot of memory (over 100mb according to the PHP manual). While the above code is a trivial demonstration, there are plenty of real-world situations where large arrays of data are constructed, often taking a long time to build and occupying a lot of memory.
With the introduction of generators, it’s now easy to tackle this problem without the inconvenience of having to write an
Iterator class. Generators do not construct a large array, but rather return a single element at a time as they are iterated. Consider this modification to the above code, now using a generator to produce the range of values:
<?php // define a simple range generator function generateRange($start, $end, $step = 1) { for ($i = $start; $i < $end; $i += $step) { // yield one result at a time yield $i; } } foreach (generateRange(0, 1000000) as $number) { echo $number; }
This code produces exactly the same result as the first example, but without producing a large array to store all the values. According to the manual, this reduces the memory footprint to less than a single kilobyte – a huge saving compared with the original example.
Password Hashing
The new password hashing API is one of the most important and useful features added in PHP 5.5. In the past, developers have had to rely on the somewhat confusing
crypt() function, which is poorly documented in the PHP manual. The introduction of a simplified set of functions to handle password hashing will make it much easier for developers to understand and implement secure password hashing for their sites.
The new API introduces two new functions,
password_hash() and
password_verify(). Calling
password_hash($password, PASSWORD_DEFAULT) will return a strong hash using bcrypt, with salting handled automatically. Verifying the password later is as easy as checking the result of
password_verify($password, $hash).
The API uses bcrypt by default, but in the future new algorithms may be introduced to provide even more secure methods of hashing. Developers can specify their own bcrypt work factor to adjust the strength of the hashes produced, and can also use their own salts instead of the automatic salt generation (although the manual discourages this).
finally
PHP 5.5 adds support for the
finally keyword, a much-requested feature found in many other languages with exception handling.
finally allows developers to specify code to be run at the end of
try and
catch blocks, regardless of whether an exception was thrown or not, before the normal execution flow resumes.
Without the
finally keyword, developers were sometimes be forced to repeat code within both the
try and
catch blocks to handle cleanup tasks. For example, in the following example the call to
releaseResource() must be made in two places:
<?php function doSomething() { $resource = createResource(); try { $result = useResource($resource); } catch (Exception $e) { releaseResource($resource); log($e->getMessage()); throw $e; } releaseResource($resource); return $result; }
With the addition of
finally, we can eliminate the duplicate code:
<?php function doSomething() { $resource = createResource(); try { $result = useResource($resource); return $result; } catch (Exception $e) { log($e->getMessage()); throw $e; } finally { releaseResource($resource); } }
In the modified version, we call the cleanup function
releaseResource() in the
finally block where we know it will always be called. Note that even though the
try block returns a value, the
finally block will still be called before the
return statement is executed and normal execution continues.
Array and String Literal Dereferencing
Array and string literals can now be dereferenced using array access syntax:
<?php // array dereferencing - returns 3 echo [1, 3, 5, 7][1]; // string dereferencing - returns "l" echo "hello"[3];
This feature was added primarily to improve the consistency of the language, and probably won’t revolutionize the way we write PHP. However, there are some interesting applications to consider, such as the following:
<?php $randomChar = "abcdefg0123456789"[mt_rand(0, 16)];
Using empty() with Function Calls and Expressions
The
empty() construct can now be used with function calls and other expressions. For example,
empty($object->getProperty()) is valid code in PHP 5.5. This makes it possible to use
empty() on the return value of functions without capturing the value in a variable first.
Class Name Resolution
Since the introduction of namespaces in PHP 5.3, it has become common practice to use extensive namespacing to organize classes in PHP projects. However, until now it has been difficult to retrieve a fully-qualified class name as a string. Consider the following code:
<?php use NamespacedClassFoo; $reflection = new ReflectionClass("Foo");
This will fail as PHP will attempt to use the global Foo class instead of the namespaced class. In PHP 5.5, it is now possible to retrieve the full namespaced class name as a string using the
class keyword:
<?php use NamespacedClassFoo; $reflection = new ReflectionClass(Foo::class);
This will now work as intended, as
Foo:class will resolve to
Namespaced\Class\Foo.
Changes to foreach
The
list() construct in PHP allows the values of an array to be easily assigned to variables. For example:
<?php $values = ["sea", "blue"]; list($object, $description) = $values; // returns "The sea is blue" echo "The $object is $description";
It’s now possible to use
list() with multidimensional arrays within
foreach loops. For example:
<?php $data = [ ["sea", "blue"], ["grass", "green"] ]; foreach ($data as list($object, $description)) { echo "The $object is $descriptionn"; } /* Outputs: The sea is blue The grass is green */
This is a powerful new feature that has the potential to make iterating through nested arrays much easier and cleaner.
foreach loops can now also handle non-scalar values as iterator keys, which means that element keys may have values that are not strings or integers.
Conclusion
PHP 5.5 offers many improvements to facilitate PHP development. In addition to new features, a long list of bugs have been resolved in this release (see the changelog for details), and various optimizations and enhancements have been made to improve performance and stability.
Will you be upgrading to PHP 5.5? Let us know in the comments.