$('.card-header h5 a').click(function() {
    $('.card-header').removeClass('active');

    //If the panel was open and would be closed by this click, do not active it
    if(!$(this).closest('.card').find('.panel-collapse').hasClass('in'))
        $(this).parents('.card-header').addClass('active');

});


<div class="box-perguntas">
    <?php
        $perguntas = get_field('perguntas');
        if ($perguntas) {
            $i = 0;
            foreach ($perguntas as $p) {
                $i++;
                ?>

                <div id="accordion" role="tablist">
                    <div class="card">
                        <div class="card-header" role="tab" id="headingOne">
                            <h5 class="mb-0">
                                <a class="btn-collapse" data-toggle="collapse" href="#id<?php echo $i; ?>" role="button" aria-expanded="true" aria-controls="id<?php echo $i; ?>">
                                    0<?php echo $i . '. ' . $p['titulo']; ?>

                                    <i class="fa fa-plus pull-right" aria-hidden="true"></i>
                                </a>
                            </h5>
                        </div>

                        <div id="id<?php echo $i; ?>" class="collapse panel-collapse" role="tabpanel" aria-labelledby="headingOne" data-parent="#accordion">
                            <div class="card-body">
                                <p><?php echo $p['texto']; ?></p>
                            </div>
                        </div>
                    </div>
                </div>

                <?php
            }
        }
    ?>
</div>