character limit in mobile view using php

I'm trying to find out how to limit the characters on the mobile display using php. I have made the character limit (700 characters) work fine. I want the character limit on the mobile display to be 150 characters. How do I implement it in PHP?

PHP (Laravel)

@if (strlen($val->getByLang('id')->description) > 700)
    <div class="section-description desc-more">
        {!! substr($val->getByLang('id')->description, 0, 700).'...' !!}
        <span class="view-more">Read More</span>
    </div>
    <div class="section-description desc-full" style="display: none;">
        {!! $val->getByLang('id')->description !!}
        <span class="view-less">Show Less</span>
    </div>
@else
    <div class="section-description">
        {!! $val->getByLang('id')->description !!}
    </div>
@endif

Javascript

$('.view-more').on('click', function () {
    $('.desc-more').hide();
    $('.desc-full').show();
});

$('.view-less').on('click', function () {
    $('.desc-full').hide();
    $('.desc-more').show();
});