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Easy processing chain creation for PHP

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Octocat-spinner-32 lib
Octocat-spinner-32 tests
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Octocat-spinner-32 README.md
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README.md

Plumber

Library for easily creating processing chains.

Inspired and influenced by TinkerPop Pipes

Author: Josh Adell josh.adell@gmail.com
Copyright (c) 2011-2012

Build Status

Usage

$msg = array(72,0,101,108,108,111,44,32,0,87,111,114,108,0,100,33);

$pipeline = new Everyman\Plumber\Pipeline();
$pipeline->filter()->transform(function ($v) { return chr($v); });

foreach ($pipeline($msg) as $c) {
  echo $c;
}

Install

Composer is the recommended way to install Plumber. Add the following to your composer.json:

{
    "require": {
        "everyman/plumber": "dev-master"
    }
}

Purpose

Often times, it is necessary to loop through a list, filter out unneeded values, and perform one or more transformations on the remaining values. A good example of this is reading and formatting records from a database:

$users = // code to retrieve user records from a database as an array or Iterator...

$names = array();
foreach ($users as $user) {
    if (!$user['first_name'] || !$user['last_name']) {
        continue;
    }

    $name = $user['first_name'] . ' ' . $user['last_name'];
    $name = ucwords($name);
    $name = htmlentities($name);
    $names[] = $name;
}

// later on, display the names
foreach ($names as $name) {
    echo "$name<br>";
}

There are several downsides to this process:

  • Looping through the list more than once
  • Requiring the whole data set in memory at once
  • Process steps are not reusable

Using a "deferred processing pipe", the values aren't transformed until they are needed, on demand:

$users = // code to retrieve user records from a database...

$names = new Everyman\Plumber\Pipeline();
$names->filter(function ($user) { return $user['first_name'] && $user['last_name']; })
    ->transform(function ($user) { return $user['first_name'] . ' ' . $user['last_name']; })
    ->transform('ucwords')
    ->transform('htmlentities');

// later on, display the names
foreach ($names($users) as $name) {
    echo "$name<br>";
}

Built-in Pipes

Plumber comes with several pre-built pipes that can be used immediately.

Filter

filter pipes remove values from the data to avoid further processing. Without providing a filter function, the filter pipe strips out values that cast to boolean false:

$pipeline->filter();
foreach ($pipeline(array(0, 1, false, true, '', 'abc', null, array(), array())) as $value) {
    echo $value.' ';
}
// Output: 1 1 abc Array

You can provide a filter function to use. The function should take 2 parameters, the value and key of the current element. If the function returns a truthy value, the element will continue to the next processing step:

$pipeline->filter(function ($value, $key) {
    return $key % 2;
});
foreach ($pipeline(array(0, 1, 2, 9, 10, 67)) as $value) {
    echo $value.' ';
}
// Output: 0 2 10

Filter pipes are the basis of several other built-in pipes.

Unique

unique pipes filter out any value that has previsouly been seen during processing:

$pipeline->unique();
foreach ($pipeline(array('foo', 'bar', 'baz', 'foo', 'baz', 'qux')) as $value) {
    echo $value.' ';
}
// Output: foo bar baz qux

Slice

slice pipes return values after a given offset and up to a given length:

$pipeline->slice(2,3);
foreach ($pipeline(array('foo', 'bar', 'baz', 'qux', 'lorem', 'ipsum')) as $value) {
    echo $value.' ';
}
// Output: baz quz lorem

If the second parameter is left off, all values after the offset are returned:

$pipeline->slice(1);
foreach ($pipeline(array('foo', 'bar', 'baz', 'qux', 'lorem', 'ipsum')) as $value) {
    echo $value.' ';
}
// Output: bar baz quz lorem ipsum

Random

random pipes emit values randomly based on a threshold. The threshold should be between 0 and 100, and represents the chance in 100 that a value will be emitted:

$pipeline->random(40);
foreach ($pipeline(array('foo', 'bar', 'baz', 'qux', 'lorem', 'ipsum')) as $value) {
    echo $value.' ';
}
// Possible output: bar ipsum

Transform

transform pipes manipulate the incoming value and emit the output of the manipulation. Without providing a transform function, the pipe will emit every value as is:

$pipeline->transform();
foreach ($pipeline(array('foo', 'bar', 'baz', 'qux', 'lorem', 'ipsum')) as $value) {
    echo $value.' ';
}
// Output: foo bar baz qux lorem ipsum

A transformation function should take 2 parameters, the current value and key in the pipeline:

$pipeline->transform(function ($value, $key) {
    return strrev($value);
});
foreach ($pipeline(array('foo', 'bar', 'baz', 'qux', 'lorem', 'ipsum')) as $value) {
    echo $value.' ';
}
// Output: oof rab zab xuq merol muspi

Pluck

pluck pipes emit a single value (or an array of values) taken from an array or object:

$pipeline->pluck('id');
$data = array(
    array('id' => 123, 'foo' => 'bar'),
    array('id' => 456, 'baz' => 'qux'),
    array('lorem' => 'ipsum'),
);
foreach ($pipeline($data) as $key => $value) {
    echo $key.':'.$value.' ';
}
// Output: 0:123 1:456 2:

If an array of keys is given, the emitted value will be an array containing each key and the values for those keys. The values of any keys not found will be null.

IfElse

ifElse pipes are used to emit a value if a certain condition is met, and a different value if the condition is not met:

$pipeline->ifElse(function ($value, $key) { return strlen($value) < 4; },
    function ($value, $key) { return -1; },
    function ($value, $key) { return strlen($value); }
);
foreach ($pipeline(array('zero', 'one', 'two', 'three', 'four', 'five', 'six')) as $value) {
    echo $value.' ';
}
// Output: 4 -1 -1 5 4 4 -1

If the third callback (the "else" callback) is omitted, then the value will be passed through "as-is" if the condition is not met:

$pipeline->ifElse(function ($value, $key) { return strlen($value) < 4; },
    function ($value, $key) { return -1; }
);
foreach ($pipeline(array('zero', 'one', 'two', 'three', 'four', 'five', 'six')) as $value) {
    echo $value.' ';
}
// Output: zero -1 -1 three four five -1

Custom Pipes

It is possible to build your own pipe to perform custom logic. The pipe should extend one of the built-in pipes, typically Everyman\Plumber\Pipe\TransformPipe or Everyman\Plumber\Pipe\FilterPipe. If you do not extend one of the built-in pipes, you must extend Everyman\Plumber\Pipe.

class MyCustomPipe extends Everyman\Plumber\Pipe\TransformPipe
{
    public function __construct()
    {
        parent::__construct(function ($value, $key) use () {
            // do custom logic
            return $customValue;
        });
    }
}

$pipeline = new Everyman\Plumber\Pipeline();
$pipeline->appendPipe(new MyCustomPipe());

It is also possible to register custom pipe classes so that they may be used with the fluent pipe interface:

Everyman\Plumber\Helper::registerPipe('custom', 'MyCustomPipe');

$pipeline = new Everyman\Plumber\Pipeline();
$pipeline->custom();

Note that the name of the pipe does not have to match the class name. Also, the registered class name must be the fully-qualified class name.

If multiple custome pipes are all under the same namespace and each pipe class name ends with "Pipe", the entire namespace can be registered:

namespace My\Project\Pipes;

class MyCustomPipe extends Everyman\Plumber\Pipe\TransformPipe { ... }

class AnotherPipe extends Everyman\Plumber\Pipe\TransformPipe { ... }

Everyman\Plumber\Helper::registerNamespace('My\Project\Pipes');

$pipeline = new Everyman\Plumber\Pipeline();
$pipeline->myCustom()->another();

Note that when registering a namespace, the method called on the pipeline is the name of the class, lower camel-cased, and without the 'Pipe' suffix. If all pipes in the namespace have a suffix other than 'Pipe', that suffix can be passed as a second parameter to registerNamespace. The second parameter can be the empty string if there is a not a common suffix.

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