Souke/backend/views/user/mail.php

<?php

use yii\helpers\Html;
use yii\bootstrap\ActiveForm;

/* 
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

$this->title = 'Envoi d\'un email à tous les utilisateurs';

?>

<h1><?= Html::encode($this->title) ?></h1>

<?php

$form = ActiveForm::begin(['id' => 'email-masse-form','enableClientValidation' => false]); ?>
    <?= $form->field($model, 'subject') ?>
    <?= $form->field($model, 'body')->textArea(['rows' => 6]) ?>

    <div class="form-group">
        <label class="control-label">Envoyer à</label>
        <p>Cliquer sur les utilisateurs pour modifier leur état.<br />
            Légende : <span class="label label-default">à envoyer</span> <span class="label label-danger">ne pas envoyer</span> <span class="label label-success">envoyé</span></p>
        <div id="ids-users">
        <?php foreach($users as $u): ?>
            <a href="javascript:void(0);" class="label <?php if($u->no_mail): ?>label-danger<?php else: ?>label-default<?php endif; ?>" data-send="0" data-id="<?php echo $u->id; ?>"><?php echo Html::encode($u->prenom.' '.$u->nom); ?></a>
        <?php endforeach; ?>
        </div>
        <input name="id_user" type="hidden" value="" />
    </div>
    <br />

    <div class="form-group">
        <?= Html::submitButton('Envoyer', ['class' => 'btn btn-default', 'name' => 'email-masse-button']) ?>
    </div>
<?php ActiveForm::end(); ?>