To get a horizontal scrollbar appear (and prevent the <pre><code>
object from overlapping the sidebar) you need to add the d-block
class (display:block) to the media element.
Here's a working code snippet (click the "run code snippet" button below and expand to full page):
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<div class="container pt-5">
<div class="row">
<div class="col-8" id="main">
<div class="media d-block">
<div class="media-body">
<h5 class="mt-0">Media heading</h5>
Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
<pre class="code" style="background: #f1f1f1;"><code class="php"><span style="color: #0275d8; font-weight: bold;">if</span><span style="color: #A67f59;">(</span> <span style="color: #04527F;">$line_numbers</span> <span style="color: #A67f59;">&&</span> <span style="color: #04527F;">$line_numbers</span> <span style="color: #A67f59;">!==</span> <span style="color: #707070;">'false'</span> <span style="color: #A67f59;">)</span> <span style="color: #A67f59;">{</span>
<span style="color: #04527F;">$output</span> <span style="color: #A67f59;">.=</span> <span style="color: #707070;">'<div class="line_numbers">'</span><span style="color: #A67f59;">;</span>
<span style="color: #04527F;">$line_count</span> <span style="color: #A67f59;">=</span> <span style="color: #0275d8; font-weight: bold;">substr_count</span><span style="color: #A67f59;">(</span> <span style="color: #04527F;">$code</span><span style="color: #A67f59;">,</span> <span style="color: #707070;">"<span style="color: #000099; font-weight: bold;">\n</span>"</span> <span style="color: #A67f59;">)</span><span style="color: #A67f59;">;</span>
<span style="color: #04527F;">$line_start</span> <span style="color: #A67f59;">=</span> <span style="color: #A67f59;">(</span> <span style="color: #0275d8; font-weight: bold;">is_numeric</span><span style="color: #A67f59;">(</span> <span style="color: #04527F;">$line_numbers</span> <span style="color: #A67f59;">)</span> ? <span style="color: #04527F;">$line_numbers</span> <span style="color: #A67f59;">:</span> <span style="color: #70B9EF;">1</span> <span style="color: #A67f59;">)</span><span style="color: #A67f59;">;</span>
<span style="color: #0275d8; font-weight: bold;">for</span><span style="color: #A67f59;">(</span> <span style="color: #04527F;">$i</span> <span style="color: #A67f59;">=</span> <span style="color: #70B9EF;">0</span><span style="color: #A67f59;">;</span> <span style="color: #04527F;">$i</span> <span style="color: #A67f59;"><=</span> <span style="color: #04527F;">$line_count</span><span style="color: #A67f59;">;</span> <span style="color: #04527F;">$i</span><span style="color: #A67f59;">++</span> <span style="color: #A67f59;">)</span> <span style="color: #A67f59;">{</span>
<span style="color: #0275d8; font-weight: bold;">if</span><span style="color: #A67f59;">(</span> is_tax<span style="color: #A67f59;">(</span> <span style="color: #707070;">'files'</span> <span style="color: #A67f59;">)</span> <span style="color: #A67f59;">)</span>
<span style="color: #A67f59;">{</span>
<span style="color: #04527F;">$output</span> <span style="color: #A67f59;">.=</span> <span style="color: #707070;">'<span id="L'</span> <span style="color: #A67f59;">.</span> <span style="color: #0275d8; font-weight: bold;">sprintf</span><span style="color: #A67f59;">(</span><span style="color: #707070;">"<span style="color: #009933; font-weight: bold;">%02d</span>"</span><span style="color: #A67f59;">,</span> <span style="color: #04527F;">$i</span> <span style="color: #A67f59;">+</span> <span style="color: #70B9EF;">1</span> <span style="color: #A67f59;">)</span> <span style="color: #A67f59;">.</span> <span style="color: #707070;">'">'</span> <span style="color: #A67f59;">.</span> <span style="color: #A67f59;">(</span> <span style="color: #04527F;">$line_start</span> <span style="color: #A67f59;">+</span> <span style="color: #04527F;">$i</span> <span style="color: #A67f59;">)</span> <span style="color: #A67f59;">.</span> <span style="color: #707070;">"</span><span style="color: #000099; font-weight: bold;">\n</span>"</span><span style="color: #A67f59;">;</span>
<span style="color: #A67f59;">}</span>
<span style="color: #0275d8; font-weight: bold;">else</span>
<span style="color: #A67f59;">{</span>
<span style="color: #04527F;">$output</span> <span style="color: #A67f59;">.=</span> <span style="color: #A67f59;">(</span> <span style="color: #04527F;">$line_start</span> <span style="color: #A67f59;">+</span> <span style="color: #04527F;">$i</span> <span style="color: #A67f59;">)</span> <span style="color: #A67f59;">.</span> <span style="color: #707070;">"<span style="color: #000099; font-weight: bold;">\n</span>"</span><span style="color: #A67f59;">;</span>
<span style="color: #A67f59;">}</span>
<span style="color: #A67f59;">}</span>
<span style="color: #04527F;">$output</span> <span style="color: #A67f59;">.=</span> <span style="color: #707070;">'</div>'</span><span style="color: #A67f59;">;</span>
<span style="color: #A67f59;">}</span></code></pre>
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