A Laravel 5.2 trait that stores a value in the session that can be used with a form select to set the per page value for a length aware paginator.

PerPageTrait.php

<?php

namespace App\Traits;

use Illuminate\Http\Request;

/**
 * A Laravel 5.2 trait that stores a value in the session that can be used with
 * a form select to set the per page value for a length aware paginator.
 *
 * @author Al Warren
 *        
 */
trait PerPageTrait
{
	/**
	 * Determin if the session key needs to be removed
	 *
	 * @param string $key        	
	 * @param mixed $perPage        	
	 * @param number $perPageDefault        	
	 *
	 * @return mixed
	 */
	public function requestResetsPerPage($key, $perPage, $perPageDefault) {
		$result = false;
		
		$perPage = is_numeric( $perPage ) ?( int ) $perPage : $perPage;
		
		if($perPage == $perPageDefault || request()->exists( $key ) && empty( $perPage ))
			$result = true;
		
		return $result;
	}
	
	/**
	 * Validate the request value.
	 *
	 * @param mixed $perPage        	
	 * @param mixed $perPageDefault        	
	 * @param number $maxPerPage        	
	 *
	 * @return mixed
	 */
	public function validPerPageRequest($perPage, $perPageDefault, $maxPerPage) {
		if(is_numeric( $perPage ))
			$perPage =( int ) substr( $perPage, 0, strlen(( string ) $maxPerPage ) );
		
		if(is_numeric( $perPage ) && $perPage > $maxPerPage)
			$perPage = 'all';
		
		if($perPage && ! is_numeric( $perPage ) && $perPage !== 'all')
			return false;
		
		return $perPage;
	}
	
	/**
	 * Store the request value in a session if needed and return
	 * the value, an existing session value, or a default.
	 *
	 * @param mixed $perPageDefault        	
	 * @param number $maxPerPage        	
	 * @param string $key        	
	 *
	 * @return mixed
	 */
	public function perPageRequest($perPageDefault = 50, $maxPerPage = 49, $key = 'per_page') {
		$perPageRequest = strtolower( trim( request()->get( $key ) ) );
		
		if($this->requestResetsPerPage( $key, $perPageRequest, $perPageDefault ))
			session()->forget( $key );
		
		$perPage = $this->validPerPageRequest( $perPageRequest, $perPageDefault, $maxPerPage );
		if(false === $perPage)
			abort( 400, 'Bad Per Page Request' );
		
		$sessionPerPage = request()->session()->get( $key );
		if($sessionPerPage && empty( $perPage ))
			return $sessionPerPage;
		
		if($perPage !== $perPageDefault)
			request()->session()->put( $key, $perPage );
		
		return( $perPage ?: $perPageDefault );
	}
}

Controller:

<?php
namespace App\Http\Controllers\Test;

use App\Http\Controllers\Controller;
use App\Traits\PerPageTrait;
use App\User;

class UsersController extends Controller
{
    use PerPageTrait;
    
    public function index()
    {
        $per_page = session('per_page') ?: config('settings.per_page.default');
        
        $users = $per_page == 'all' ? User::all() : User::paginate($per_page) ;
         
        return view('test.users', compact('users', 'per_page'));
    }
    
    public function postPerPage()
    {
        $this->perPageRequest(config('settings.per_page.default'), User::count());
         
        return redirect()->back();
    }
}

Routes:

Route::group(
    ['prefix' => 'test',
        'middleware' => ['auth', 'acl'],
        'is' => 'administrator', // from Kodin ACL (acl)
    ],
    function() {
        Route::get('users', 'Test\UsersController@index');
        Route::post('users', 'Test\UsersController@postPerPage');
    }
);

Form:

<form class="form-inline" action="{{ request()->url() }}" method="post">
    {!! csrf_field() !!}
    <label for="per_page">Per Page:</label>
    <select class="form-control form-control-sm" id="per_page" name="per_page" onchange="this.form.submit()">
        @foreach ( config('settings.per_page.options') as $option )
        <option value="{{ $option }}"{{ $option == $per_page ? ' selected' : '' }}>{{ $option }}</option>
        @endforeach
    </select>
</form>