Installation issue with Laravel 5.2

[mahmouddev]

I tried to install laravel-omnipay via composer :composer require barryvdh/laravel-omnipayI get :

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Conclusion: remove symfony/event-dispatcher v3.2.4
    - Conclusion: don't install symfony/event-dispatcher v3.2.4
    - omnipay/common 2.4.0 requires guzzle/guzzle ~3.9 -> satisfiable by guzzle/guzzle[v3.9.0, v3.9.1, v3.9.2, v3.9.3].
    - omnipay/common 2.5.2 requires guzzle/guzzle ~3.9 -> satisfiable by guzzle/guzzle[v3.9.0, v3.9.1, v3.9.2, v3.9.3].
    - omnipay/common v2.3.4 requires guzzle/guzzle ~3.9 -> satisfiable by guzzle/guzzle[v3.9.0, v3.9.1, v3.9.2, v3.9.3].
    - omnipay/common v2.4.1 requires guzzle/guzzle ~3.9 -> satisfiable by guzzle/guzzle[v3.9.0, v3.9.1, v3.9.2, v3.9.3].
    - omnipay/common v2.5.0 requires guzzle/guzzle ~3.9 -> satisfiable by guzzle/guzzle[v3.9.0, v3.9.1, v3.9.2, v3.9.3].
    - omnipay/common v2.5.1 requires guzzle/guzzle ~3.9 -> satisfiable by guzzle/guzzle[v3.9.0, v3.9.1, v3.9.2, v3.9.3].

[HubertSadecki]

Run the command below before
composer require symfony/event-dispatcher:^2.8
according to this