Migrating a PHP 5 App to PHP 7 (Rundown of PHP 7 Features)

TL;DR: Many PHP applications are still running on PHP 5.x, not ready to take full advantage of the awesome features that PHP 7 offers. A lot of developers have not made the switch because of certain fears of compatibility issues, migration challenges and the strange awkward feeling that migrating will take away a big chunk of their time. In the first part of this tutorial we learned how to set up a PHP 7 development environment. This time, we'll learn about all the new PHP 7 features and how you can leverage them when migrating your PHP 5 app to PHP 7.

PHP 7 Features

Scalar Type Declaration

With PHP 5, you could typehint a function parameter with Classes, Interfaces, callable and array types only. For example, if you want a parameter of a certain type string to be passed into a function, you would have to do a check within the function like so:

// php 5
function getBookNo($number) {
    if (! is_integer($number)) {
        throw new Exception("Please ensure the value is a number");
    }

    return $number;
}

getBookNo('boooks');

PHP 7 eliminates the need for the extra check. With PHP 7, you can now typehint your function parameters with string, int, float, and bool.

// PHP 7
function getBookNo(int $number) {
    return $number;
}

getBookNo('boooks');

// Error raised
PHP Fatal error:  Uncaught TypeError: Argument 1 passed to getBookNo() must be of the type integer, string given, called in ....

PHP 7 will throw a Fatal error as seen above once you typehint with scalar values.

Strong Type Check

By default, PHP 5 and 7 allow for coercion when dealing with operations such as numeric strings. An example is this:

function getBookNo(int $number) {
    return "This is it: " . $number;
}

echo getBookNo("8");

// Result
This is it: 8

I passed in a string and it coerced it to an integer and allowed it to run successfully. Now in PHP 7, you can be strict and ensure no form of automatic conversion occurs by declaring a strict mode at the top of your PHP file like so:

declare(strict_types=1);

function getBookNo(int $number) {
    return "This is it: " . $number;
}

echo getBookNo("8");

// Result
PHP Fatal error:  Uncaught TypeError: Argument 1 passed to getBookNo() must be of the type integer, string given, called in ......

In PHP 5, if you pass in a float value, it automatically strips out the decimal parts and leaves you with an integer. Now in PHP 7, If you pass in a float value too, it will throw a Fatal error. When building a financial application, this feature comes in handy!

Remember something like this in JavaScript? where you have to write use "strict"; at the top of your JavaScript file.

Return Type Declaration

PHP 7 supports return types for functions. This feature has been available in several strongly typed languages for a long time. Now, you can easily enforce a function to return a certain type of data like so:

function divideValues(int $firstNumber, int $secondNumber): int {
    $value = $firstNumber / $secondNumber;
    return $value;
}

echo divideValues(8, 9);

// Result
0

In the function above, we want the return value to be an integer, regardless of whatever the division turns out to be. Now the default weak(coercive) type checking in PHP comes to play again here. The value returned should be a float and it should throw a Fatal Type Error but it is automatically coerced into an integer.

Enable strict mode by placing declare(strict_types=1); at the top of the file and run it again. It should throw a PHP Fatal Type error like so:

PHP Fatal error:  Uncaught TypeError: Return value of divideValues() must be of the type integer, float returned in .....

Spaceship Operator

PHP 7 ships with a new operator, <=>, for simplifying the evaluation of arithmetic operations. With this operator, it is easier to evaluate less than, equal to, or greater than. The results will either be -1, 0 or 1. Ruby and PERL programmers are familiar with this operator.

This is how it works. If we have two operands $x and $y, and we do $x <=> $y, then

if $x is less than $y, the result will be -1
if $x equals $y, the result will be 0
if $x is greater than $y, the result will be 1

function evaluate($x, $y) {
    return $x <=> y;
}

evaluate(9, 8);

// Result
1

Good real world cases for this operator is in the simplification of comparison methods and using it for switch operations like so:

$data = [
   ['name' => 'Ado', 'cars' => 2],
   ['name' => 'Tony', 'cars' => 4],
   ['name' => 'Ramirond', 'cars' => 3],
   ['name' => 'Woloski', 'cars' => 12]
];

function sortByCars($x, $y) {
    return $x['cars'] <=> $y['cars'];
}

usort($data, 'sortByCars');

print_r($data);

// Result
Array
(
    [0] => Array
        (
            [name] => Ado
            [cars] => 2
        )

    [1] => Array
        (
            [name] => Ramirond
            [cars] => 3
        )

    [2] => Array
        (
            [name] => Tony
            [cars] => 4
        )

    [3] => Array
        (
            [name] => Woloski
            [cars] => 12
        )

)

It sorted the array easily with less code. Without the spaceship operator, I would have to write the sortByCars method like so:

function sortByCars($x, $y)
{
    if ($x['cars'] == $y['cars']) {
        return 0;
    }

    return ($x['cars'] < $y['cars']) ? -1 : 1;
}

Array Constants

Before now, constants defined with the define() method can only accept scalar values. In PHP 7, you can have constant arrays using the define() method like so:

// PHP 7
define('CARS', [
    'fine' => 'Mercedes',
    'strong' => 'Volkswagen',
    'ugly' => 'chevrolet'
]);

echo CARS['fine'];

// Result
Mercedes

Group Use Declarations

Group use declaration helps make the code shorter and simpler. Before now, if you are trying to use multiple classes, functions and constants from the same namespace, you have to write it like so:

// PHP 5
namespace Unicodeveloper\Emoji;

use Unicodeveloper\Emoji\Exceptions\UnknownMethod;
use Unicodeveloper\Emoji\Exceptions\UnknownEmoji;
use Unicodeveloper\Emoji\Exceptions\UnknownUnicode;
use Unicodeveloper\Emoji\Exceptions\UnknownIsNull;
use function Unicodeveloper\Emoji\Exceptions\checkForInvalidEmoji;
use const Unicodeveloper\Emoji\Exceptions\INVALID_EMOJI;

class Emoji {

}

With PHP 7, you can group them like so:

// PHP 7
namespace Unicodeveloper\Emoji;

use Unicodeveloper\Emoji\Exceptions\{
    UnknownMethod, UnknownEmoji, UnknownUnicode, IsNull, function checkForInvalidEmoji, const INVALID_EMOJI };

class Emoji {

}

Anonymous Classes

An Anonymous class is essentially a local class without a name. Anonymous classes offer the ability to spin up throwaway objects. These objects have closure-like capabilities. An anonymous class is defined like so:

new class($constructor, $args) {

}

A real world case is a situation where you want to have objects that implement some interfaces on the fly, rather than having several files, where you have to define the class and then instantiate it, you can leverage anonymous classes like so:

$meme = new class implements MemeInterface {
    public function memeForm($form) {
      return $form;
    }
};

$app = new App($meme);

Enhanced Unicode Support

In PHP 7, all you need is the hexadecimal code appended to "\u" and you'll have your symbol/emoji as an output. An example is this:

function getMoney() {
    echo "\u{1F4B0}";
}

getMoney();

// Result
💰

The enhancements were made possible from the Unicode Codepoint Escape Syntax RFC.

Now, you can also get the name equivalent of the unicode character, say "\u{1F4B0}" via the new IntlChar class like so:

echo IntlChar::charName("\u{1F4B0}");

You can get the character from the name like so:

var_dump(IntlChar::charFromName("LATIN CAPITAL LETTER A"));
var_dump(IntlChar::charFromName("SNOWMAN"));
var_dump(IntlChar::charFromName("TURTLE"));

Note: The IntlChar class contains about 600 constants and 59 static methods.

This was made possible from the IntlChar RFC. The PHP manual has extensive documentation on IntlChar class.

Null Coalescing Operator

The purpose of this new operator, ??, is to allow developers to set values from user inputs without having to check if the value has been set. Before PHP 7, this is how you evaluate input. Check this out:

$occupation = isset($_GET['occupation']) ? $_GET['occupation'] : 'bricklayer';

If the value of $_GET['occupation'] exists, it returns the value else it assigns bricklayer to the $occupation variable. In PHP 7, you can simply shorten that line of code using the ?? operator like so:

// PHP 7
$occupation = $_GET['occupation'] ?? 'bricklayer';

It automatically checks whether the value is set and assigns the value to $occupation variable if it is, else it returns bricklayer.

The Null coalescing operator also allows you to chain expressions like so:

// PHP 7

$_ENV['occupation'] = 'software engineer';

$occupation = isset($_GET['occupation']) ?? $_ENV['occupation'] ?? 'bricklayer';

// Result
software engineer

This will assign the first defined value to the $occupation variable.

Closure on Call

There is now a better and more performant way of binding an object scope to a closure and calling it. Before PHP 7, you would bind an object to a closure like so:

class NameRegister {
    private $name = "Prosper";
}

// Closure
$getName = function() {
    return $this->name;
};

$getTheName = $getName->bindTo(new NameRegister, 'NameRegister');
echo $getTheName();

With PHP 7, you now have a call method on the Closure class. So you can bind an object to a closure easily like so:

class NameRegister {
    private $name = "Prosper";
}

$getName = function() {
    echo $this->name;
};

$getName->call(new NameRegister());

Check out the PHP Manual: Closure::call for more information.

Expectations and Assertions

Assertions are a debugging and development feature. The assert() function in PHP 7 is now a language construct, where the first parameter can also be an expression instead of just been a string or boolean. They have been optimized to have zero cost in production. You can now enable or disable assertions from the PHP_INI file like so:

zend.assertions = 1 // Enable assertion
zend.assertions = 0 // Disable assertion
zend.assertions = -1 // (production mode), don't generate or execute code

Assertions can now throw an Exception when it fails. You can enable that from the INI file like so:

assert.exceptions = 1 // Throw exceptions

// or

assert.exceptions = 0 // Issue warnings, which has always been the case.

The assert() can now take in two arguments where the second argument is a custom error message. It can also be an instance of an Exception. An example is shown below:

class ProjectException extends AssertionError {}

public function checkAuthenticityOfProject() {

    /* ... */

    assert('$project instanceof \Unicodeveloper\Project', new ProjectException('$project was not a Project object'));
}

Note: With this new feature, you might not need to depend on assertion libraries anymore while developing and testing your code.

Check out the Expectations RFC for more information.

Error Handling

Many fatal and recoverable fatal errors have been converted to exceptions in PHP 7. Most errors are now reported by throwing Error exceptions. The Exception class now implements a Throwable Interface.

Hierarchy

\Throwable
├── \Exception (implements \Throwable)
│   ├── \LogicException
|   │   │ \BadFunctionCallException
│   |   |  └── \BadMethodCallException
│   │   |── \DomainException
|   |   ├── \InvalidArgumentException
|   |   ├── \LengthException
|   |   └── \OutOfRangeException
│   │  
│   |   
|   └── \RuntimeException
│       ├── \OutOfBoundsException
│       ├── \OverflowException
│       ├── \RangeException
│       ├── \UnderflowException
│       └── \UnexpectedValueException
└── \Error (implements \Throwable)
    ├── \AssertionError
    ├── \ArithmeticError
    ├── \DivisionByZeroError
    ├── \ParseError
    └── \TypeError

So you can catch specific Errors like so:

try {
    // evaluate something
} catch (\ParseError $e) {
   // do something
}

Earlier in this article, we were evaluating scalar type hinting and PHP 7 threw TypeErrors. Remember? Yes, that's how cool PHP 7 is now!

In PHP 7.1, you can catch multiple errors and exceptions in one catch block like so:

try {
   // Some code...
} catch (ExceptionTypeA | ExceptionTypeB | ExceptionTypeC $e) {
   // Code to handle the exception
} catch (\Exception $e) {
   // ...
}

This is particular useful when one method throws different type of exceptions that you can handle the same way.

Note: A new error_clear_last() method has been added to clear the most recent error. Once used, calling error_get_last() will be unable to retrieve the most recent errors.

Check out the Catching Multiple Exception Types RFC.

Integer Division

PHP 7 introduced a new function intdiv() which returns the result of an integer division operation as int.

// PHP 7
$result = intdiv(10, 4);

// Result:
2

Regular Expressions

Handling regular expressions just got easier in PHP 7. A new preg_replace_callback_array() function has been added to perform a regular expression search and replace using callbacks.

$message = 'Haaaalaaaaaa, Girls and people of Instagrant';

preg_replace_callback_array(
    [
        '~[a]+~i' => function ($match) {
            echo strlen($match[0]), ' matches for "a" have been found';
        },
        '~[b]+~i' => function ($match) {
            echo strlen($match[0]), ' matches for "b" found';
        },
        '~[p]+~i' => function ($match) {
            echo strlen($match[0]), ' matches for "p" found';
        }
    ],
    $message
);


// Result
4 matches for "a" have been found
6 matches for "a" have been found
1 matches for "a" have been found
1 matches for "a" have been found
1 matches for "a" have been found
1 matches for "p" found
1 matches for "p" found

Filtered unserialize()

The unserialize() function has been existing since PHP 4. It allows you to take a single serialized variable and convert back into a PHP value.

In PHP 7, the options parameter has been added. You can now whitelist classes that can be unserialized like so:

// converts all objects into __PHP_Incomplete_Class object
unserialize($obj, ["allowed_classes" => false]);

// converts all objects into __PHP_Incomplete_Class object except those of FirstClass and SecondClass
unserialize($obj, ["allowed_classes" => ["FirstClass", "SecondClass"]]);

// default behaviour (same as omitting the second argument) that accepts all classes
unserialize($obj, ["allowed_classes" => true]);

It was introduced to enhance security when unserializing objects on untrusted data.

Note: In PHP 7.1, the allowed_classes element of the options parameter is now strictly typed. unserialize() returns false if anything other than an array or boolean is given.

Cryptographically Secure Pseudorandom Number Generator (CSRPNG)

random_bytes() and random_int() have been added to the CSRPNG functions in PHP 7.

random_bytes() returns a random string of a given length
random_int() returns a random integer from a range

random_bytes(12);

random_int(0, 5000);

Generator Delegation and Return Expressions

Generators were introduced in PHP 5.5. Prior to PHP 7, if you tried to return anything, an error would be thrown. Now, you can use a return statement within a generator.

You can get the returned value by calling the Generator::getReturn() method. Look at the code below:

$square = function (array $number) {
    foreach($number as $num)
    {
        yield $num * $num;
    }  

    return "Done calculating the square. What next?";  
};

$result = $square([1,2,3,4,5]);

foreach($result as $value)
{
  echo $value . PHP_EOL;
}

echo $result->getReturn(); // grab the return value

// RESULT
1
4
9
16
25
Done calculating the square. What next?

Generators can now delegate to another generator by using yield from like so:

function square(array $number) {
    foreach($number as $num)
    {
        yield $num * $num;
    }  

    yield from addition($number);
};

function addition(array $number) {
    foreach($number as $num)
    {
        yield $num + $num;
    }  
}

foreach(square([1,2,3,4,5]) as $value)
{
  echo $value . PHP_EOL;
}

// Result
1
4
9
16
25
2
4
6
8
10

session_start config enhancements

The session_start() method now accepts an array of values that can override the session config in php.ini file.

session.lazy_write which is on by default can be turned off by explicitly stating it in the session_start() method like so:

session_start([
    'lazy_write' => false,
    'cache_limiter' => 'private'
]);

Unpack objects with list()

The list() language construct now allows you to unpack objects implementing the ArrayAccess interface.

$fruits = new ArrayObject(['banana', 'mango', 'apple']);

list($a, $b, $c) = $fruits;

echo $a. PHP_EOL;
echo $b. PHP_EOL;
echo $c. PHP_EOL;

// Result
banana
mango
apple

Note: In PHP 7.0.0 list() expressions can no longer be completely empty. In PHP 5, list() assigns the values starting with the right-most parameter. In PHP 7, list() starts with the left-most parameter. This is true when working with arrays with indices.

Accessing Static Values

In PHP 5.x, if you try to access a static value like so:

class Auth0 {
    static $lock = 'v10';
}

echo 'Auth0'::$lock;

// Result
Parse error: syntax error, unexpected '::' (T_PAAMAYIM_NEKUDOTAYIM), expecting ',' or ';' in .....

Now, In PHP 7.x, it throws no error, it simply works!

// PHP 7

class Auth0 {
    static $lock = 'v10';
}

echo 'foo'::$lock;

// Result
v10

dirname() enhancement

The dirname() in PHP 5 returns a parent directory's path. In PHP 7.0.0, an optional levels parameter has been added to the function to allow you as developer determine how many levels up you want to go when getting a path.

$path = '/Unicodeveloper/source/php-workspace/laravel/vavoom';

dirname($path, 3);

// Result
/Unicodeveloper/source

Uniform Variable Syntax

This brings a much needed change to the way variable-variable expressions are constructed. It allows for a number of new combinations of operators that were previously disallowed, and so introduces new ways to achieve old operations in a more polished code.

// nesting ::
$foo::$bar::$baz // access the property $baz of the $foo::$bar property

// nesting ()
foo()() // invoke the return of foo()

// operators on expressions enclosed in ()
(function () {})() // IIFE syntax from JS

                        // old meaning            // new meaning
$$foo['bar']['baz']     ${$foo['bar']['baz']}     ($$foo)['bar']['baz']
$foo->$bar['baz']       $foo->{$bar['baz']}       ($foo->$bar)['baz']
$foo->$bar['baz']()     $foo->{$bar['baz']}()     ($foo->$bar)['baz']()
Foo::$bar['baz']()      Foo::{$bar['baz']}()      (Foo::$bar)['baz']()

Reserved Words

PHP 7 now allows globally reserved words such as new, private, for as property, constant, and method names within classes, interfaces, and traits.

class Car {

    private $type, $who, $costs;

    public function new($carType) {
        $this->type = $carType;
        return $this;
    }

    public function for($who) {
        $this->who = $who;
        return $this;
    }

    public function costs($price) {
        $this->price = $price;
        return $this;
    }

    public function __toString() {
        return $this->type . ' ' . $this->who . ' ' . $this->price. PHP_EOL;
    }
}

$car = new Car();
echo $car->new('Mercedes Benz')->for('Wife')->costs(14000);

// Result
Mercedes Benz Wife 14000

Reflection API Enhancements

PHP 7 introduces two new reflection classes. One is the ReflectionGenerator class that reports information about generators and the other is the ReflectionType class that reports information about a function's return type.

ReflectionType API

ReflectionType::allowsNull — Checks if null is allowed
ReflectionType::isBuiltin — Checks if it is a built-in type
ReflectionType::__toString
- gets the parameter type name

ReflectionGenerator API

ReflectionGenerator::__construct — Constructs a ReflectionGenerator object
ReflectionGenerator::getExecutingFile — Gets the file name of the currently executing generator
ReflectionGenerator::getExecutingGenerator — Gets the executing Generator object
ReflectionGenerator::getExecutingLine — Gets the currently executing line of the generator
ReflectionGenerator::getFunction — Gets the function name of the generator
ReflectionGenerator::getThis — Gets the $this value of the generator
ReflectionGenerator::getTrace — Gets the trace of the executing generator

Two new methods have also been added to the ReflectionParameter and ReflectionFunctionAbstract classes.

ReflectionParameter API

ReflectionParameter::hasType
- Checks if parameter has a type
ReflectionParameter::getType
- Gets a parameter's type

ReflectionFunctionAbstract API

ReflectionFunctionAbstract::hasReturnType
- Checks if the function has a specified return type.
ReflectionFunctionAbstract::getReturnType — Gets the specified return type of a function

Deprecated Features

Using deprecated features in PHP will trigger an E_DEPRECATED error.

PHP 4 Style constructors are deprecated, and will be removed in the future. An example of a PHP 4 style of writing constructors(having the same name with the class) is this:
```
  class Economy {
      function economy() {
          /* ... */
      }
  }
```

Static calls to methods that are actually not static are deprecated.

  class Economy {
      function affordPrimaryEducation() {
          echo 'I think I might not be able to afford it with this economy';
      }
  }

  Economy::affordPrimaryEducation();

  // Result
  Deprecated: Non-static method Economy::affordPrimaryEducation() should not be called statically in ......

The salt option for the password_hash() function has been deprecated to prevent developers from generating their own salts which are mostly insecure.
The capture_session_meta SSL context option has been deprecated. stream_get_meta_data() can now be used to get SSL metadata.
The ldap_sort() function has been deprecated.
The alternative PHP tags shown below have been removed:
PHP Script tags
```
  <script language="php">
  </script>
```
PHP ASP tags
```
  <% %>
```

Backward Incompatible Changes

Here are backward incompatible changes you should be aware of:

setexceptionhandler() is no longer guaranteed to receive Exception objects
Internal constructors always throw exceptions on failure: Prior to PHP 7, some internal classes would return NULL when the constructor failed. Now, they will throw an Exception.
Error handling for eval() should now include a catch block that can handle the ParseError object.
The almighty E_STRICT notices now have new behaviors. It's no longer too strict.
list() can no longer unpack string variables. str_split() should be used when performing this form of operation.
global can no longer accept variable variables unless you fake it by using the curly brace like so global ${$foo->bar}.
An E_WARNING will be emitted and NULL will be returned when internal functions try to perform float to integer automatic conversions.
Prefixing comments with # in php.ini file is no longer allowed. Only semi-colons(;) should be used.
Dividing by 0 will emit an E_WARNING and also one of either +INF, -INF, or NAN.
$HTTP_RAW_POST_DATA was deprecated in PHP 5.6.0 and finally removed in PHP 7.0.0. Use php://input as a replacement.
Switch statements can no longer have multiple default blocks. An ECOMPILEERROR will be triggered if you try to define more than one default block.
Functions can not have multiple parameters with the same name. function slap($hand, $hand, $strength). An ECOMPILEERROR will be triggered as a result of this function.
Static calls made to a non-static method with an incompatible context will now result in the called method having an undefined $this variable and a deprecation warning being issued.

You can check out the few other PHP core functions that have changed.

Removed Extensions and SAPIs

The ext/mysql, ext/mssql, ereg and sybase_ct extensions have been removed. All the mysql_ functions have been removed! You should either use the ext/mysqli extension or use the ext/pdo extension which is has an object-oriented API.

The aolserver, apache, apache_hooks, apache2filter, caudium, continuity, isapi, milter, nsapi, phttpd, pi3web, roxen, thttpd, tux and webjames SAPIs have been removed.

Conclusion

We have successfully covered all the new features of PHP 7. It might be overwhelming at first because it is a major version with a lot of new features, and lots of deprecations.

Going over the rundown of all these features as highlighted in this article and using it as a handy reference will give you all the necessary information to migrate your PHP 5 apps to PHP 7.

Thanks to the PHP Manual and RFC documents. You can always reference them for more information.

In the next and final part of this series, we'll convert a small PHP 5 app to PHP 7, then measure and report the performance difference.

Looking for the best way to secure your PHP projects? Auth0 offers a generous free tier to get started with modern authentication. This modern tool provides the simplest and easiest to use User interface tools to help administrators manage user identities including password resets, creating and provisioning, blocking and deleting users.

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Migrating a PHP 5 App to PHP 7 (Rundown of PHP 7 Features) - Part 2