Clean up the section on running other commands

Author: stevegrunwell

slides.md

@@ -667,33 +667,21 @@ The most common ways you'll see PHP call other scripts
 
 <dl>
     <dt><a href="https://www.php.net/manual/en/function.system.php"><code>system()</code></a></dt>
-    <dd></dd>
+    <dd>Returns last line of output, flushes buffer as it goes</dd>
     <dt><a href="https://www.php.net/manual/en/function.passthru.php"><code>passthru()</code></a></dt>
-    <dd>Returns raw output</dd>
     <dd>Best choice for binary files</dd>
 </dl>
 
 Note:
 
 * `system()`
+    * Works the same as its C equivalent
+    * Will attempt to flush the output buffer as it goes, but only returns the last line (and can set exit code to a variable by reference)
 * `passthru()` doesn't attempt to transform the output, so this is really useful when working within binary files like images, video, etc.
     * Link in slides' README explaining how I used it to generate animated thumbnails for gifs
 
 ----
 
-### Calling other scripts
-
-<dl>
-    <dt><a href="https://www.php.net/manual/en/function.proc-open.php"><code>proc_open()</code></a></dt>
-    <dd></dd>
-    <dt><a href="https://www.php.net/manual/en/function.pcntl-exec.php"><code>pcntl_exec()</code></a></dt>
-    <dd></dd>
-</dl>
-
-Note:
-
-----
-
 <!-- .slide: data-background-image="resources/spidey-sense.png" data-background-position="left bottom" data-background-size="contain" data-hide-footer -->
 
 Note:
@@ -1076,6 +1064,23 @@ Note:
 
 ----
 
+### Don't let scripts be run from a browser!
+
+If your commands live within the web root, prevent them from being run outside the CLI:
+
+```php
+// Prevent this script from being run outside of a CLI context
+if (PHP_SAPI !== 'cli') {
+    exit;
+}
+```
+
+Note:
+
+Modern frameworks keep most app code out of the web root, but if you're writing commands that will live under the web root **be sure that they can't be executed by a web request!**
+
+----
+
 ### Swanson on Commands
 
 ![Ron Swanson (Nick Offerman) advising "Never half-ass two things. Whole-ass one thing."](resources/whole-ass.gif)