✔ engine improvements

• 100%+ performance gain on most real-world applications
• Lower memory usage, sometimes drastically lower

JIT?

Improve CPU cache usage

• Step 1: Decrease overall data
• Step 2: Better data locality and less indirections
• Step 3: Save the world!

• zval size reduced from 24 to 16 bytes
• Hashtable size reduced from 72 to 56 bytes
• Hashtable bucket size reduced from 72 to 32 bytes
• Immutable array optimization

$a = [];
for($i=0; $i < 100000;$i++) {
    $a[] = ['abc','def','ghi','jkl','mno','pqr'];
}
echo memory_get_usage(true);

// PHP 5.x  109M
// PHP 7.0   42M no opcache
// PHP 7.0    6M with opcache enabled

• New memory allocator similar to jemalloc
• Faster hashtable iteration API
• Array duplication optimization
• PCRE JIT enabled by default
• Precomputed string hashes
• Fast ZPP (ZendParseParameters) implementation
• Faster stack-allocated zvals (instead of heap)
• Optimized VM calling
• Global register variables with gcc 4.8+
• plus hundreds of micro-optimizations

HugePage support in Opcache

./configure --enable-huge-code-pages

opcache.memory_consumption=256
opcache.huge_code_pages=1

% sysctl -w vm.nr_hugepages=256
% service php-fpm start
% cat /proc/meminfo | grep Huge
HugePages_Total:     256
HugePages_Free:      231
HugePages_Rsvd:      119
HugePages_Surp:        0
Hugepagesize:       2048 kB

JIT?

GCC Feedback-Directed Optimization (FDO)

$ make clean
$ make -j8 prof-gen
...
$ sapi/cgi/php-cgi -T 1000 /var/www/wordpress/index.php > /dev/null
$ make prof-clean
$ make -j8 prof-use

✔ engine improvements

• 100%+ performance gain on most real-world applications
• Lower memory usage, sometimes drastically lower

✔ Exceptions on Fatals

function call_method($obj) {
    $obj->method();
}
call_method(null);

Fatal error: Uncaught Error: Call to a member function method() on null in file:2
Stack trace:
#0 file(4): call_method(NULL)
#1 {main}
  thrown in file on line 2

try {
    call_method(null);
} catch (Error $e) {
    echo "Caught Exception: {$e->getMessage()}\n";
}

Caught Exception: Call to a member function method() on null

PHP 7 Exception Hierarchy

• Throwable
• ➥ Exception implements Throwable
• ➥ Error implements Throwable
• ➥ TypeError extends Error
• ➥ ParseError extends Error

✔ Return Types

function get_config(): array {
    return 42;
}
get_config();

Fatal error: Uncaught TypeError: Return value of get_config() must be
of the type array, integer returned in file:2
Stack trace:
#0 file(4): get_config()
#1 {main}
  thrown in file on line 2

✔ Coercive Scalar Types

function logmsg(string $msg, int $level, float $severity) {
    var_dump($msg);      // string(1) "1"
    var_dump($level);    // int(2)
    var_dump($severity); // float(3)
}
logmsg(1, "2.5 bananas", 3);

Notice: A non well formed numeric value encountered in file on line 2

✔ Strict Scalar Types

declare(strict_types=1);
...
logmsg(1, "2.5", 3);

Fatal error: Uncaught TypeError: Argument 1 passed to logmsg() must be of the
type string, integer given, called in file on line 7 and defined in file:3
Stack trace:
#0 file(7): logmsg(1, '2.5', 3)
#1 {main}
  thrown in file on line 2

✔ Anonymous Classes

return new class($controller) implements Page {
    public function __construct($controller) {
        /* ... */
    }
    /* ... */
};

class MyObject extends MyStuff {
    public function getInterface() {
        return new class implements MyInterface {
            /* ... */
        };
    }
}

✔ Coalesce Operator

$a = NULL;
$b = 0;
$c = 2;

echo $a ?? $b; // 0
echo $c ?? $b; // 2
echo $a ?? $b ?? $c; // 0
echo $a ?? $x ?? $c; // 2

✔ Spaceship Operator

function cmp_php5($a, $b) {
    return ($a < $b) ? -1 : (($a >$b) ? 1 : 0);
}

function cmp_php7($a, $b) {
    return $a <=> $b;
}

✔ Removal of many deprecated features
     (Your PHP4 code will break!)

- ext/ereg (use ext/pcre instead)
- preg_replace() eval modifier (use preg_replace_callback() instead)
- ext/mysql (use ext/mysqli or ext/pdo_mysql instead)
- Assignment of new by reference
- Scoped calls of non-static methods from incompatible $this context

- dl() in php-fpm
- set_magic_quotes_runtime() and magic_quotes_runtime()
- set_socket_blocking() (use stream_set_blocking() instead)
- mcrypt_generic_end() (use mcrypt_generic_deinit() instead)
- mcrypt_ecb, mcrypt_cbc, mcrypt_cfb and mcrypt_ofb 
  (use mcrypt_encrypt() and mcrypt_decrypt() instead)
- datefmt_set_timezone_id() and IntlDateFormatter::setTimeZoneID() 
  (use datefmt_set_timezone() or IntlDateFormatter::setTimeZone() instead)

- xsl.security_prefs (use XsltProcessor::setSecurityPrefs() instead)
- iconv.input_encoding, iconv.output_encoding, iconv.internal_encoding,
  mbstring.http_input, mbstring.http_output and mbstring.internal_encoding
  (use php.input_encoding, php.internal_encoding and php.output_encoding instead)

- $is_dst parameter of the mktime() and gmmktime() functions
- # style comments in ini files (use ; style comments instead)
- String category names in setlocale() (use LC_* constants instead)
- Unsafe curl file uploads (use CurlFile instead)
- PDO::PGSQL_ATTR_DISABLE_NATIVE_PREPARED_STATEMENT driver option 
  (use PDO::ATTR_EMULATE_PREPARES instead)
- CN_match and SNI_server_name stream context option (use peer_name instead)

✔ New reserved words:

• bool
• int
• float
• string
• null
• false
• true
• resource
• object
• mixed
• numeric

✔ 64-bit integer support on Windows

✔ Cleanup edge-case integer overflow/underflow

✔ Support for strings with length >= 2^31 bytes in 64 bit builds.

✔ Parse error on invalid numeric literals

$mask = 0855;  // Parse error: Invalid numeric literal

✔ Uniform variable syntax

// left-to-right
$this->$belongs_to['column']
// vs.
$this->{$belongs_to['column']}

// support missing combinations of operations
$foo()['bar']()
[$obj1, $obj2][0]->prop
getStr(){0}
 
// support nested ::
$foo['bar']::$baz
$foo::$bar::$baz
$foo->bar()::baz()
 
// support nested ()
foo()()
$foo->bar()()
Foo::bar()()
$foo()()
 
// support operations on arbitrary (...) expressions
(...)['foo']
(...)->foo
(...)->foo()
(...)::$foo
(...)::foo()
(...)()
 
// two more practical examples for the last point
(function() { ... })()
($obj->closure)()
 
// support all operations on dereferencable scalars
// (not very useful)
"string"->toLower()
[$obj, 'method']()
'Foo'::$bar

✔ Unicode Codepoint Escape Syntax

echo "\u{202E}Right-to-left text";

echo " \u{26BD}";

‮Right-to-left text ⚽		

✔ ICU IntlChar class added to intl extension

✔ CSPRNG

$int   = random_int(-500, 500);
$bytes = random_bytes(10);

var_dump( $int );
var_dump( bin2hex($bytes) );

int(348)
string(20) "9576ce9260bcaa4509b5"
		

Top-5 Things that might bite you

For the full list see

Left-to-right semantics for complicated expressions

$$foo['bar']['baz'] // interpreted as ($$foo)['bar']['baz']
$foo->$bar['baz']   // interpreted as ($foo->$bar)['baz']
$foo->$bar['baz']() // interpreted as ($foo->$bar)['baz']()
Foo::$bar['baz']()  // interpreted as (Foo::$bar)['baz']()

To restore the previous behaviour add explicit curly braces:

${$foo['bar']['baz']}
$foo->{$bar['baz']}
$foo->{$bar['baz']}()
Foo::{$bar['baz']}()

Detection: phan or unit test failures

Removed support for /e (PREG_REPLACE_EVAL) modifier

echo preg_replace('/:-:(.*?):-:/e', '$this->pres->\\1', $text);

Change to:

echo preg_replace_callback(
  '/:-:(.*?):-:/', 
  function($matches) {
    return $this->pres->{$matches[1]}; // Careful!
  },
  $text);

Detection: grep, warnings in logs or unit test failures

$HTTP_RAW_POST_DATA global removed

if (empty($GLOBALS['HTTP_RAW_POST_DATA']) &&
    strpos($_SERVER['CONTENT_TYPE'], 'www-form-urlencoded') === false) {
    $GLOBALS['HTTP_RAW_POST_DATA'] = file_get_contents("php://input");
}

Detection: grep, warnings in logs or unit test failures

session.lazy_write enabled by default

session.lazy_write = 0

Detection: Can cause out-of-band session read timing issues

Invalid octal literals now produce a parse error

echo 05678; // PHP 5.x outputs 375

Parse error: Invalid numeric literal in file.php on line 2		

Detecting parse errors is easy: php -l

Let's deploy it!

Atomic

No performance hit

• No restarts
• No LB removal
• No thundering herd
• Cache reuse

Must be able to serve two versions of the site concurrently!

Requests that begin on DocumentRoot A must finish on A

Set the DocumentRoot to symlink target!

Easy with nginx

fastcgi_param DOCUMENT_ROOT $realpath_root

Apache

Avoid hardcoding full paths

Watch your include_path setting

incpath extension can resolve your include_path for you

Version all static assets

DB Schema changes need special care

PHP 7 in production

PHP 7.1

✔ void return type

function should_return_nothing(): void {
    return 1; // Fatal error: A void function must not return a value
}

✔ Nullable types

function answer(int $a, ?int $b): ?int  {
    if($a > $b) return $a;
    else return null;
}

✔ Iterable pseudo-type

function foo(iterable $iterable) {
    foreach ($iterable as $value) {
        // ...
    }
}
function bar(): iterable {
    return [1, 2, 3];
}

✔ Negative string offsets

$str='abcdef';
var_dump($str[-2]); // => string(1) "e"

✔ List keys

list($first, $second, $third) = [1, 2, 3];
[$first, $second, $third] = [1, 2, 3];

✔ Warn about invalid strings in arithmetic

$numberOfApples = "10 apples" + "5 pears";

Notice: A non well formed numeric string encountered in example.php on line 2
Notice: A non well formed numeric string encountered in example.php on line 2

✔ Class constant visibility

class Token {
    // Constants default to public
    const PUBLIC_CONST = 0;
 
    private const PRIVATE_CONST = 0;
    protected const PROTECTED_CONST = 0;
    public const PUBLIC_CONST_TWO = 0;

✔ Things that may break your code

• new 'void' and 'iterable' keywords
• rand() and srand() are now aliased to mt_rand() and mt_srand()
• Calling a function with too few args is now an Error instead of a Warning
• Dropped support for sslv2 streams
• Dropped support for mcrypt

Thank You

Report Bugs

Useful bug reports, please!