• A class like User very common 
• A 3rd party library can cause these sorts of naming conflicts

trait Hello {
    function sayHello() {
        return "Hello";
    }
}
trait World {
    function sayWorld() {
        return "World";
    }
}
class MyWorld {
    use Hello, World;
}
 
$world = new MyWorld();
echo $world->sayHello() . " " . $world->sayWorld(); //Hello World

function doMath(callable $function, $a, $b)
{
    return $function($a, $b);
}

doMath(function($a, $b) { return $a * $b; }, 9, 2); // 18

function sum ($a, $b)
{
    return $a + $b;
}

$division = function($a, $b)
{
    return $a/$b;
};

function doMath(Closure $function, $a, $b)
{
    return $function($a, $b);
}

doMath($division, 9, 3); // 3

$division = function($a, $b)
{
    return $a/$b;
};

function doMath(Closure $function, $a, $b)
{
    $result = $function($a, $b);
    return function() use ($result) {echo $result;};
}

$callback = doMath($division, 9, 3);
$callback(); // 3

• Copy / Paste
• Do it yourself
• Git Submodules

• Your app depends on libraries
• Keep these libraries up to date
• Libraries also depend on other libraries

• Resolves inter-package dependencies
• Installs all dependencies
  
• Create an autoloader
• Follows PSR-0 and PSR-4
• Inspired by
• Node.JS NPM
• Ruby Bundler

curl -s https://getcomposer.org/installer | php

curl -s https://getcomposer.org/rinstaller | php
sudo mv composer.phar /usr/local/bin/composer

1. Create a sample project and 
2. Add a composer.json  file
   
3. Require specifies packages and version

{
    "require": {
    "php": ">=5.4",
        "guzzlehttp/guzzle": "4.0.*"
    }
} 

<?php
// test.php
require_once __DIR__.'/vendor/autoload.php';
$client = new GuzzleHttp\Client();

$response = $client->get('https://google.com');
echo $response->getBody();

• Finds commonalities between different Open Source  projects 
• Develop standards to better work together
  

• These are recommendations
  
• PSR-0 The Basic Autoloader
• PSR-1 Basic Coding Standards
• PSR-2 Coding Style Guide
• PSR-3 Logging
• PSR-4 Autoloader Revised
  

\{Vendor Name}\({Namespace}\)*{Class Name} 

use Foo\Bar\Database\Model;
use Custom\Database\Model as CustomModel;

class MyController {
    $model = new Model();
    $customModel = new CustomModel();
}

namespace Vendor\Package;
                                                  // <== Line break
use OtherVendor\OtherPackage\BazClass;
                                                  // <== Line break      
class Foo extends Bar implements FooInterface
{                                                 // <== Brace in new line
    public $var;                                  // <== Visibility 

    public function sampleFunction($a, $b = null) // <== Must not have space
    {                                             // <== Brace in new line
        if ($a === $b) {                          // <== Brace in same line
            bar();                                // <== 4 space indentation
        } else {
            BazClass::bar($arg2, $arg3);
        }
    }                                             // <== Must be in new line
}

These are amongst the least know functionality  in the SPL, yet they can be very helpful.

Data structures implement the Iterator and Countable interfaces which enable them to be traversed using foreach() and counted using the count().

Some notable Data Structures are:

• SplDoublyLinkedList
  
• SplHeap
• SplFixedArray

• You can move forward or backwards
• Memory efficient
• Random reads can be slower that array
• Can be used as a queue or a stack
  

• Complete binary tree that satisfy the heap property
• Can insert directly into stored position under ideal conditions
  
• Is an abstract class
• Must implement class compare
• Return 1 if value 1 > value 2
• Return 0 if value 1 == value 2
• Return -1 if value 1 < value2
• You can compare anything, these definitions are up to you
  

class Test {
    public function __destruct(){
        echo "Destroying class ".__CLASS__;
    }
}

$array = new \SplFixedArray(6);
$array[5] = new Test();
$array->setSize(5); // Destroying class Test