Added information/examples about input checking (#21615)

* Added information/examples about input checking

* removed boilerplate

guide/english/php/forms/checking-required-inputs/index.md

@@ -1,13 +1,21 @@
 ---
 title: Checking Required Inputs
 ---
+
 ## Checking Required Inputs
 
-This is a stub. <a href='https://github.com/freecodecamp/guides/tree/master/src/pages/php/forms/checking-required-inputs/index.md' target='_blank' rel='nofollow'>Help our community expand it</a>.
+PHP has a few functions to check if the required inputs have been met. Those functions are ```isset```, ```empty```, and ```is_numeric```.
 
-<a href='https://github.com/freecodecamp/guides/blob/master/README.md' target='_blank' rel='nofollow'>This quick style guide will help ensure your pull request gets accepted</a>.
+### Checking form to make sure its set
+The ```isset``` checks to see if the field has been set and isn't null.
+Example:
+```php
+$firstName = $_GET['firstName']
 
-<!-- The article goes here, in GitHub-flavored Markdown. Feel free to add YouTube videos, images, and CodePen/JSBin embeds  -->
-
-#### More Information:
-<!-- Please add any articles you think might be helpful to read before writing the article -->
+if(isset($firstName)){
+  echo "firstName field is set". "<br>";
+}
+else{
+  echo "The field is not set."."<br>";
+}
+```