$string = 'String of text that you want to shorten';

// Starts at the beginning of the string and ends after 100 characters
echo substr($string, 0, 100).'... <a href="page.php">Read More</a>';

echo '<p id="hide'.$id.'" class="cby" style="padding-left: 5px;">';

echo '
<script type="text/javascript">
function showHide'.$id.'()
{
$("div#show'.$id.'").toggle(100);
$("p#hide'.$id.'").css("display", "none");
}
</script>

<a Onclick="showHide'.$id.'()">   » Devamını Oku..! </a>
  <div id="show'.$id.'" class="cby" style="padding-left: 5px; display:none;">'.$tablodaki_icerik_adi.'</div></p>';

 <section class="space light">
        <div class="container container-custom">
            <div class="row">
                <div class="col-md-12">
                    <div class="heading-style1">
                        <span>Blog ----</span>
                        <h2>Son Yazılar</h2>
                    </div>
                </div>
            </div>
            <div class="row">
                <div class="col-md-12">
                    <div class="service-slider blog-slider">
                        <?php $bloggetir = $db->query("SELECT * FROM blog")->fetchAll(PDO::FETCH_ASSOC);
                        foreach ($bloggetir as $blog) { ?>
                        <div class="blog-grid-wrap">
                            <div class="blog-grid-img">
                                <img src="panel/<?=$blog['blogresim']?>" class="img-fluid" alt="#">
                            </div>
                            <div class="blog-grid_content">
                                <div class="blog-grid-top_icon">
                                    <label><?=$blog['blogkategori']?></label>
                                    <p><?=$blog['blogtarih']?></p>
                                </div>
                                <div class="blog-grid_text">
                                    <a href=" blog/<?=$blog['bloglink']?>.html">
                                        <h4><?=$blog['blogbaslik']?></h4>
                                    </a>
                                    <p><?=$blog['blogicerik']?> </p>
                                </div>
                            </div>
                        </div>
                        <?php } ?>
                    </div>
                </div>
            </div>
        </div>
    </section>