PHP 7 Programming Cookbook

Chapter 1. Building a Foundation

In this chapter, we will cover the following topics:

PHP 7 installation considerations
Using the built-in PHP web server
Defining a test MySQL database
Installing PHPUnit
Implementing class autoloading
Hoovering a website
Building a deep web scanner
Creating a PHP 5 to PHP 7 code converter

PHP 7 installation considerations

There are three primary means of acquiring PHP 7:

Downloading and installing directly from the source code
Installing pre-compiled binaries
Installing a *AMP package (that is, XAMPP, WAMP, LAMP, MAMP, and so on)

How to do it...

The three methods are listed in order of difficulty. However, the first approach, although tedious, will give you the most finite control over extensions and options.

Installing directly from source

In order to utilize this approach, you will need to have a C compiler available. If you are running Windows, MinGW is a free compiler that has proven popular. It is based on the GNU Compiler Collection (GCC) compiler provided by the GNU project. Non-free compilers include the classic Turbo C compiler from Borland, and, of course, the compiler that is preferred by Windows developers is Visual Studio. The latter, however, is designed mainly for C++ development, so when you compile PHP, you will need to specify C mode.

When working on an Apple Mac, the best solution is to install the Apple Developer Tools. You can use the Xcode IDE to compile PHP 7, or run gcc from a terminal window. In a Linux environment, from a terminal window, run gcc.

When compiling from a terminal window or command line, the normal procedure is as follows:

configure
make
make test
make install

For information on configuration options (that is, when running configure), use the help option:

configure --help

Errors you might encounter during the configuration stage are mentioned in the following table:

Error

Fix

configure: error: xml2-config not found. Please check your libxml2 installation

You just need to install libxml2. For this error, please refer to the following link:

http://superuser.com/questions/740399/how-to-fix-php-installation-when-xml2-config-is-missing

configure: error: Please reinstall readline - I cannot find readline.h

Install libreadline-dev

configure: WARNING: unrecognized options: --enable-spl, --enable-reflection, --with-libxml

Not a big deal. These options are defaults and don't need to be included. For more details, please refer to the following link:

http://jcutrer.com/howto/linux/how-to-compile-php7-on-ubuntu-14-04

Installing PHP 7 from pre-compiled binaries

As the title implies, pre-compiled binaries are a set of binary files that somebody else has kindly compiled from PHP 7 source code and has made available.

In the case of Windows, go to http://windows.php.net/. You will find a good set of tips in the left column that pertain to which version to choose, thread safe versus non-read safe, and so forth. You can then click on Downloads and look for the ZIP file that applies to your environment. Once the ZIP file has been downloaded, extract the files into the folder of your choice, add php.exe to your path, and configure PHP 7 using the php.ini file.

To install the pre-compiled binaries on a Mac OS X system, it is best to involve a package management system. The ones recommended for PHP include the following:

MacPorts
Liip
Fink
Homebrew

In the case of Linux, the packaging system used depends on which Linux distribution you are using. The following table, organized by Linux distribution, summarizes where to look for the PHP 7 package.

Distribution	Where to find PHP 7	Notes
Debian	`packages.debian.org/stable/php` `repos-source.zend.com/zend-server/early-access/php7/php-7DEB`	Use this command: sudo apt-get install php7 Alternatively, you can use a graphical package management tool such as Synaptic. Make sure you select php7 (and not php5).
Ubuntu	`packages.ubuntu.com` `repos-source.zend.com/zend-server/early-access/php7/php-7DEB`	Use this command: `sudo apt-get install php7` Be sure to choose the right version of Ubuntu. Alternatively, you can use a graphical package management tool such as Synaptic.
Fedora / Red Hat	`admin.fedoraproject.org/pkgdb/packages` `repos-source.zend.com/zend-server/early-access/php7/php-7RHEL`	Make sure you are the root user: su Use this command: dnf install php7 Alternatively, you can use a graphical package management tool such as the GNOME Package Manager.
OpenSUSE	`software.opensuse.org/package/php7`	Use this command: yast -i php7 Alternatively, you can run `zypper`, or use YaST as a graphical tool.

Installing a *AMP package

AMP refers to Apache, MySQL, and PHP (also Perl and Python). The * refers to Linux, Windows, Mac, and so on (that is, LAMP, WAMP, and MAMP). This approach is often the easiest, but gives you less control over the initial PHP installation. On the other hand, you can always modify the php.ini file and install additional extensions to customize your installation as needed. The following table summarizes a number of popular *AMP packages:

Package	Where is it found	Free?	Supports*
`XAMPP`	www.apachefriends.org/download.html	Y	WML
`AMPPS`	www.ampps.com/downloads	Y	WML
`MAMP`	www.mamp.info/en	Y	WM
`WampServer`	sourceforge.net/projects/wampserver	Y	W
`EasyPHP`	www.easyphp.org	Y	W
`Zend Server`	www.zend.com/en/products/zend_server	N	WML

In the preceding table, we've enlisted the *AMP packages where * is replaced by W for Windows, M for Mac OS X, and L for Linux.

There's more...

When you install a pre-compiled binary from a package, only core extensions are installed. Non-core PHP extensions must be installed separately.

It's worth noting that PHP 7 installation on cloud computing platforms will often follow the installation procedure outlined for pre-compiled binaries. Find out if your cloud environment uses Linux, Mac, or Windows virtual machines, and then follow the appropriate procedure as mentioned in this recipe.

It's possible that PHP 7 hasn't yet reached your favorite repository for pre-compiled binaries. You can always install from source, or consider installing one of the *AMP packages (see the next section). An alternative for Linux-based systems is to use the Personal Package Archive (PPA) approach. Because PPAs have not undergone a rigorous screening process, however, security could be a concern. A good discussion on security considerations for PPAs is found at http://askubuntu.com/questions/35629/are-ppas-safe-to-add-to-my-system-and-what-are-some-red-flags-to-watch-out-fo.

Defining a test MySQL database

For test purposes, along with the source code for the book, we've provided an SQL file with sample data at https://github.com/dbierer/php7cookbook. The name of the database used in the recipes for this book is php7cookbook.

How to do it...

Define a MySQL database, php7cookbook. Also assign rights to the new database to a user called cook with the password book. The following table summarizes these settings:

Item

Notes

Database name

php7cookbook

Database user

cook

Database user password

book

Here is an example of SQL needed to create the database:

CREATE DATABASE IF NOT EXISTS dbname DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
CREATE USER 'user'@'%' IDENTIFIED WITH mysql_native_password;
SET PASSWORD FOR 'user'@'%' = PASSWORD('userPassword');
GRANT ALL PRIVILEGES ON dbname.* to 'user'@'%';
GRANT ALL PRIVILEGES ON dbname.* to 'user'@'localhost';
FLUSH PRIVILEGES;

Import the sample values into the new database. The import file, php7cookbook.sql, is located at https://github.com/dbierer/php7cookbook/blob/master/php7cookbook.sql.

Implementing class autoloading

When developing PHP using an object-oriented programming (OOP) approach, the recommendation is to place each class in its own file. The advantage of following this recommendation is the ease of long-term maintenance and improved readability. The disadvantage is that each class definition file must be included (that is, using include or its variants). To address this issue, there is a mechanism built into the PHP language that will autoload any class that has not already been specifically included.

Getting ready

The minimum requirement for PHP autoloading is to define a global __autoload() function. This is a magic function called automatically by the PHP engine when a class is requested but where said class has not been included. The name of the requested class will appear as a parameter when __autoload() is invoked (assuming that you have defined it!). If you are using PHP namespaces, the full namespaced name of the class will be passed. Because __autoload() is a function, it must be in the global namespace; however, there are limitations on its use. Accordingly, in this recipe, we will make use of the spl_autoload_register() function, which gives us more flexibility.

How to do it...

The class we will cover in this recipe is Application\Autoload\Loader. In order to take advantage of the relationship between PHP namespaces and autoloading, we name the file Loader.php and place it in the /path/to/cookbook/files/Application/Autoload folder.
The first method we will present simply loads a file. We use file_exists() to check before running require_once(). The reason for this is that if the file is not found, require_once() will generate a fatal error that cannot be caught using PHP 7's new error handling capabilities:
```
protected static function loadFile($file)
{
    if (file_exists($file)) {
        require_once $file;
        return TRUE;
    }
    return FALSE;
}
```
We can then test the return value of loadFile() in the calling program and loop through a list of alternate directories before throwing an Exception if it's ultimately unable to load the file.
Tip
You will notice that the methods and properties in this class are static. This gives us greater flexibility when registering the autoloading method, and also lets us treat the Loader class like a Singleton.

Next, we define the method that calls loadFile() and actually performs the logic to locate the file based on the namespaced classname. This method derives a filename by converting the PHP namespace separator \ into the directory separator appropriate for this server and appending .php:

public static function autoLoad($class)
{
    $success = FALSE;
    $fn = str_replace('\\', DIRECTORY_SEPARATOR, $class) 
          . '.php';
    foreach (self::$dirs as $start) {
        $file = $start . DIRECTORY_SEPARATOR . $fn;
        if (self::loadFile($file)) {
            $success = TRUE;
            break;
        }
    }
    if (!$success) {
        if (!self::loadFile(__DIR__ 
            . DIRECTORY_SEPARATOR . $fn)) {
            throw new \Exception(
                self::UNABLE_TO_LOAD . ' ' . $class);
        }
    }
    return $success;
}

Next, the method loops through an array of directories we call self::$dirs, using each directory as a starting point for the derived filename. If not successful, as a last resort, the method attempts to load the file from the current directory. If even that is not successful, an Exception is thrown.
Next, we need a method that can add more directories to our list of directories to test. Notice that if the value provided is an array, array_merge() is used. Otherwise, we simply add the directory string to the self::$dirs array:
```
public static function addDirs($dirs)
{
    if (is_array($dirs)) {
        self::$dirs = array_merge(self::$dirs, $dirs);
    } else {
        self::$dirs[] = $dirs;
    }
}  
```

Then, we come to the most important part; we need to register our autoload() method as a Standard PHP Library (SPL) autoloader. This is accomplished using spl_autoload_register() with the init() method:

public static function init($dirs = array())
{
    if ($dirs) {
        self::addDirs($dirs);
    }
    if (self::$registered == 0) {
        spl_autoload_register(__CLASS__ . '::autoload');
        self::$registered++;
    }
}

At this point, we can define __construct(), which calls self::init($dirs). This allows us to also create an instance of Loader if desired:
```
public function __construct($dirs = array())
{
    self::init($dirs);
}
```

How it works...

In order to use the autoloader class that we just defined, you will need to require Loader.php. If your namespace files are located in a directory other than the current one, you should also run Loader::init() and supply additional directory paths.

In order to make sure the autoloader works, we'll also need a test class. Here is a definition of /path/to/cookbook/files/Application/Test/TestClass.php:

<?php
namespace Application\Test;
class TestClass
{
    public function getTest()
    {
        return __METHOD__;
    }
}

Now create a sample chap_01_autoload_test.php code file to test the autoloader:

<?php
require __DIR__ . '/../Application/Autoload/Loader.php';
Application\Autoload\Loader::init(__DIR__ . '/..');

Next, get an instance of a class that has not already been loaded:

$test = new Application\Test\TestClass();
echo $test->getTest();

Finally, try to get a fake class that does not exist. Note that this will throw an error:

$fake = new Application\Test\FakeClass();
echo $fake->getTest();

Hoovering a website

Very frequently, it is of interest to scan a website and extract information from specific tags. This basic mechanism can be used to trawl the web in search of useful bits of information. At other times you need to get a list of <IMG> tags and the SRC attribute, or <A> tags and the corresponding HREF attribute. The possibilities are endless.

How to do it...

First of all, we need to grab the contents of the target website. At first glance it seems that we should make a cURL request, or simply use file_get_contents(). The problem with these approaches is that we will end up having to do a massive amount of string manipulation, most likely having to make inordinate use of the dreaded regular expression. In order to avoid all of this, we'll simply take advantage of an already existing PHP 7 class DOMDocument. So we create a DOMDocument instance, setting it to UTF-8. We don't care about whitespace, and use the handy loadHTMLFile() method to load the contents of the website into the object:
```
public function getContent($url)
{
    if (!$this->content) {
        if (stripos($url, 'http') !== 0) {
            $url = 'http://' . $url;
        }
        $this->content = new DOMDocument('1.0', 'utf-8');
        $this->content->preserveWhiteSpace = FALSE;
        // @ used to suppress warnings generated from // improperly configured web pages
        @$this->content->loadHTMLFile($url);
    }
    return $this->content;
}
```
Tip
Note that we precede the call to the loadHTMLFile() method with an @. This is not done to obscure bad coding (!) as was often the case in PHP 5! Rather, the @ suppresses notices generated when the parser encounters poorly written HTML. Presumably, we could capture the notices and log them, possibly giving our Hoover class a diagnostic capability as well.

Next, we need to extract the tags which are of interest. We use the getElementsByTagName() method for this purpose. If we wish to extract all tags, we can supply * as an argument:

public function getTags($url, $tag)
{
    $count    = 0;
    $result   = array();
    $elements = $this->getContent($url)
                     ->getElementsByTagName($tag);
    foreach ($elements as $node) {
        $result[$count]['value'] = trim(preg_replace('/\s+/', ' ', $node->nodeValue));
        if ($node->hasAttributes()) {
            foreach ($node->attributes as $name => $attr) 
            {
                $result[$count]['attributes'][$name] = 
                    $attr->value;
            }
        }
        $count++;
    }
    return $result;
}

It might also be of interest to extract certain attributes rather than tags. Accordingly, we define another method for this purpose. In this case, we need to parse through all tags and use getAttribute(). You'll notice that there is a parameter for the DNS domain. We've added this in order to keep the scan within the same domain (if you're building a web tree, for example):

public function getAttribute($url, $attr, $domain = NULL)
{
    $result   = array();
    $elements = $this->getContent($url)
                     ->getElementsByTagName('*');
    foreach ($elements as $node) {
        if ($node->hasAttribute($attr)) {
            $value = $node->getAttribute($attr);
            if ($domain) {
                if (stripos($value, $domain) !== FALSE) {
                    $result[] = trim($value);
                }
            } else {
                $result[] = trim($value);
            }
        }
    }
    return $result;
}

How it works...

In order to use the new Hoover class, initialize the autoloader (described previously) and create an instance of the Hoover class. You can then run the Hoover::getTags() method to produce an array of tags from the URL you specify as an argument.

Here is a block of code from chap_01_vacuuming_website.php that uses the Hoover class to scan the O'Reilly website for <A> tags:

<?php
// modify as needed
define('DEFAULT_URL', 'http://oreilly.com/');
define('DEFAULT_TAG', 'a');

require __DIR__ . '/../Application/Autoload/Loader.php';
Application\Autoload\Loader::init(__DIR__ . '/..');

// get "vacuum" class
$vac = new Application\Web\Hoover();

// NOTE: the PHP 7 null coalesce operator is used
$url = strip_tags($_GET['url'] ?? DEFAULT_URL);
$tag = strip_tags($_GET['tag'] ?? DEFAULT_TAG);

echo 'Dump of Tags: ' . PHP_EOL;
var_dump($vac->getTags($url, $tag));

The output will look something like this:

Building a deep web scanner

Sometimes you need to scan a website, but go one level deeper. For example, you want to build a web tree diagram of a website. This can be accomplished by looking for all <A> tags and following the HREF attributes to the next web page. Once you have acquired the child pages, you can then continue scanning in order to complete the tree.

How to do it...

A core component of a deep web scanner is a basic Hoover class, as described previously. The basic procedure presented in this recipe is to scan the target website and hoover up all the HREF attributes. For this purpose, we define a Application\Web\Deep class. We add a property that represents the DNS domain:
```
namespace Application\Web;
class Deep
{
    protected $domain;
```
Next, we define a method that will hoover the tags for each website represented in the scan list. In order to prevent the scanner from trawling the entire World Wide Web (WWW), we've limited the scan to the target domain. The reason why yield from has been added is because we need to yield the entire array produced by Hoover::getTags(). The yield from syntax allows us to treat the array as a sub-generator:
```
public function scan($url, $tag)
{
    $vac    = new Hoover();
    $scan   = $vac->getAttribute($url, 'href', 
       $this->getDomain($url));
    $result = array();
    foreach ($scan as $subSite) {
        yield from $vac->getTags($subSite, $tag);
    }
    return count($scan);
}
```
Note
The use of yield from turns the scan() method into a PHP 7 delegating generator. Normally, you would be inclined to store the results of the scan into an array. The problem, in this case, is that the amount of information retrieved could potentially be massive. Thus, it's better to immediately yield the results in order to conserve memory and to produce immediate results. Otherwise, there would be a lengthy wait, which would probably be followed by an out of memory error.
In order to keep within the same domain, we need a method that will return the domain from the URL. We use the convenient parse_url() function for this purpose:
```
public function getDomain($url)
{
    if (!$this->domain) {
        $this->domain = parse_url($url, PHP_URL_HOST);
    }
    return $this->domain;
}
```

How it works...

First of all, go ahead and define the Application\Web\Deep class defined previously, as well as the Application\Web\Hoover class defined in the previous recipe.

Next, define a block of code from chap_01_deep_scan_website.php that sets up autoloading (as described earlier in this chapter):

<?php
// modify as needed
define('DEFAULT_URL', unlikelysource.com');
define('DEFAULT_TAG', 'img');

require __DIR__ . '/../../Application/Autoload/Loader.php';
Application\Autoload\Loader::init(__DIR__ . '/../..');

Next, get an instance of our new class:

$deep = new Application\Web\Deep();

At this point, you can retrieve URL and tag information from URL parameters. The PHP 7 null coalesce operator is useful for establishing fallback values:

$url = strip_tags($_GET['url'] ?? DEFAULT_URL);
$tag = strip_tags($_GET['tag'] ?? DEFAULT_TAG);

Some simple HTML will display results:

foreach ($deep->scan($url, $tag) as $item) {
    $src = $item['attributes']['src'] ?? NULL;
    if ($src && (stripos($src, 'png') || stripos($src, 'jpg'))) {
        printf('<br><img src="%s"/>', $src);
    }
}

Creating a PHP 5 to PHP 7 code converter

For the most part, PHP 5.x code can run unchanged on PHP 7. There are a few changes, however, that are classified as backwards incompatible. What this means is that if your PHP 5 code is written in a certain way, or uses functions that have been removed, your code will break, and you'll have a nasty error on your hands.

Getting ready

The PHP 5 to PHP 7 Code Converter does two things:

Scans your code file and converts PHP 5 functionality that has been removed to its equivalent in PHP 7
Adds comments with // WARNING where changes in language usage have occurred, but where a re-write is not possible
Note
Please note that after running the converter, your code is not guaranteed to work in PHP 7. You will still have to review the // WARNING tags added. At the least, this recipe will give you a good head start converting your PHP 5 code to work in PHP 7.

The core of this recipe is the new PHP 7 preg_replace_callback_array() function. What this amazing function allows you to do is to present an array of regular expressions as keys, with the value representing an independent callback. You can then pass the string through a series of transformations. Not only that, the subject of the array of callbacks can itself be an array.

How to do it...

In a new class Application\Parse\Convert, we begin with a scan() method, which accepts a filename as an argument. It checks to see if the file exists. If so, it calls the PHP file() function, which loads the file into an array, with each array element representing one line:

public function scan($filename)
{
    if (!file_exists($filename)) {
        throw new Exception(
            self::EXCEPTION_FILE_NOT_EXISTS);
    }
    $contents = file($filename);
    echo 'Processing: ' . $filename . PHP_EOL;
    
    $result = preg_replace_callback_array( [

Next, we start passing a series of key/value pairs. The key is a regular expression, which is processed against the string. Any matches are passed to the callback, which is represented as the value part of the key/value pair. We check for opening and closing tags that have been removed from PHP 7:

    // replace no-longer-supported opening tags
    '!^\<\%(\n| )!' =>
        function ($match) {
            return '<?php' . $match[1];
        },

    // replace no-longer-supported opening tags
    '!^\<\%=(\n| )!' =>
        function ($match) {
            return '<?php echo ' . $match[1];
        },

    // replace no-longer-supported closing tag
    '!\%\>!' =>
        function ($match) {
            return '?>';
        },

Next is a series of warnings when certain operations are detected and there is a potential code-break between how they're handled in PHP 5 versus PHP 7. In all these cases, the code is not re-written. Instead, an inline comment with the word WARNING is added:

    // changes in how $$xxx interpretation is handled
    '!(.*?)\$\$!' =>
        function ($match) {
            return '// WARNING: variable interpolation 
                   . ' now occurs left-to-right' . PHP_EOL
                   . '// see: http://php.net/manual/en/'
                   . '// migration70.incompatible.php'
                   . $match[0];
        },

    // changes in how the list() operator is handled
    '!(.*?)list(\s*?)?\(!' =>
        function ($match) {
            return '// WARNING: changes have been made '
                   . 'in list() operator handling.'
                   . 'See: http://php.net/manual/en/'
                   . 'migration70.incompatible.php'
                   . $match[0];
        },

    // instances of \u{
    '!(.*?)\\\u\{!' =>
        function ($match) {
        return '// WARNING: \\u{xxx} is now considered '
               . 'unicode escape syntax' . PHP_EOL
               . '// see: http://php.net/manual/en/'
               . 'migration70.new-features.php'
               . '#migration70.new-features.unicode-'
               . 'codepoint-escape-syntax' . PHP_EOL
               . $match[0];
    },

    // relying upon set_error_handler()
    '!(.*?)set_error_handler(\s*?)?.*\(!' =>
        function ($match) {
            return '// WARNING: might not '
                   . 'catch all errors'
                   . '// see: http://php.net/manual/en/'
                   . '// language.errors.php7.php'
                   . $match[0];
        },

    // session_set_save_handler(xxx)
    '!(.*?)session_set_save_handler(\s*?)?\((.*?)\)!' =>
        function ($match) {
            if (isset($match[3])) {
                return '// WARNING: a bug introduced in'
                       . 'PHP 5.4 which '
                       . 'affects the handler assigned by '
                       . 'session_set_save_handler() and '
                       . 'where ignore_user_abort() is TRUE 
                       . 'has been fixed in PHP 7.'
                       . 'This could potentially break '
                       . 'your code under '
                       . 'certain circumstances.' . PHP_EOL
                       . 'See: http://php.net/manual/en/'
                       . 'migration70.incompatible.php'
                       . $match[0];
            } else {
                return $match[0];
            }
        },

Any attempts to use << or >> with a negative operator, or beyond 64, is wrapped in a try { xxx } catch() { xxx } block, looking for an ArithmeticError to be thrown:

    // wraps bit shift operations in try / catch
    '!^(.*?)(\d+\s*(\<\<|\>\>)\s*-?\d+)(.*?)$!' =>
        function ($match) {
            return '// WARNING: negative and '
                   . 'out-of-range bitwise '
                   . 'shift operations will now 
                   . 'throw an ArithmeticError' . PHP_EOL
                   . 'See: http://php.net/manual/en/'
                   . 'migration70.incompatible.php'
                   . 'try {' . PHP_EOL
                   . "\t" . $match[0] . PHP_EOL
                   . '} catch (\\ArithmeticError $e) {'
                   . "\t" . 'error_log("File:" 
                   . $e->getFile() 
                   . " Message:" . $e->getMessage());'
                   . '}' . PHP_EOL;
        },

Note

PHP 7 has changed how errors are handled. In some cases, errors are moved into a similar classification as exceptions, and can be caught! Both the Error and the Exception class implement the Throwable interface. If you want to catch either an Error or an Exception, catch Throwable.

Next, the converter rewrites any usage of call_user_method*(), which has been removed in PHP 7. These are replaced with the equivalent using call_user_func*():

    // replaces "call_user_method()" with
    // "call_user_func()"
    '!call_user_method\((.*?),(.*?)(,.*?)\)(\b|;)!' =>
        function ($match) {
            $params = $match[3] ?? '';
            return '// WARNING: call_user_method() has '
                      . 'been removed from PHP 7' . PHP_EOL
                      . 'call_user_func(['. trim($match[2]) . ',' 
                      . trim($match[1]) . ']' . $params . ');';
        },

    // replaces "call_user_method_array()" 
    // with "call_user_func_array()"
    '!call_user_method_array\((.*?),(.*?),(.*?)\)(\b|;)!' =>
        function ($match) {
            return '// WARNING: call_user_method_array()'
                   . 'has been removed from PHP 7'
                   . PHP_EOL
                   . 'call_user_func_array([' 
                   . trim($match[2]) . ',' 
                   . trim($match[1]) . '], ' 
                   . $match[3] . ');';
        },

Finally, any attempt to use preg_replace() with the /e modifier is rewritten using a preg_replace_callback():

     '!^(.*?)preg_replace.*?/e(.*?)$!' =>
    function ($match) {
        $last = strrchr($match[2], ',');
        $arg2 = substr($match[2], 2, -1 * (strlen($last)));
        $arg1 = substr($match[0], 
                       strlen($match[1]) + 12, 
                       -1 * (strlen($arg2) + strlen($last)));
         $arg1 = trim($arg1, '(');
         $arg1 = str_replace('/e', '/', $arg1);
         $arg3 = '// WARNING: preg_replace() "/e" modifier 
                   . 'has been removed from PHP 7'
                   . PHP_EOL
                   . $match[1]
                   . 'preg_replace_callback('
                   . $arg1
                   . 'function ($m) { return ' 
                   .    str_replace('$1','$m', $match[1]) 
                   .      trim($arg2, '"\'') . '; }, '
                   .      trim($last, ',');
         return str_replace('$1', '$m', $arg3);
    },

        // end array
        ],

        // this is the target of the transformations
        $contents
    );
    // return the result as a string
    return implode('', $result);
}

How it works...

To use the converter, run the following code from the command line. You'll need to supply the filename of the PHP 5 code to be scanned as an argument.

This block of code, chap_01_php5_to_php7_code_converter.php, run from the command line, calls the converter:

<?php
// get filename to scan from command line
$filename = $argv[1] ?? '';

if (!$filename) {
    echo 'No filename provided' . PHP_EOL;
    echo 'Usage: ' . PHP_EOL;
    echo __FILE__ . ' <filename>' . PHP_EOL;
    exit;
}

// setup class autoloading
require __DIR__ . '/../Application/Autoload/Loader.php';

// add current directory to the path
Application\Autoload\Loader::init(__DIR__ . '/..');

// get "deep scan" class
$convert = new Application\Parse\Convert();
echo $convert->scan($filename);
echo PHP_EOL;