PHP MySQL Where clause isn't working - php

Question

I have a database like which has multiple columns and when querying it with a WHERE clause it won't get any results.
Here is the code I am using :
$columns = $_GET['var'];
$where = $_GET['where'];
$checkValue = $_GET['checkValue'];
$userInput = $_GET['userInput'];
$query = "SELECT ";
foreach($columns as $val)
$query .= "$val, ";
$query .= "FROM Email";
if($where === "yes")
$query .= " WHERE $checkValue = '$userInput'";
$columns is multiple checkboxes for the user to select which columns they wish to see. It works perfectly except when adding the where clause. When I've been testing it I made sure that the it was exactly the same as in the database. Also the $checkValue is a dropdown list which values are exactly the same as in the database. Also just to note later on I edit the query so the last comma is removed.
To print it out I use :
while($c = mysqli_fetch_assoc($results)){
foreach($columns as $val){
$header = ucwords($val);
echo "<b>$header</b><br>";
echo $c[$val]."<br>";
}
echo "-------------------------------<br>";
}
This is the query that is outputted when not using the where clause and works:
SELECT date, mediatype FROM Email
And here is the query that doesnt work:
SELECT date, mediatype FROM Email WHERE mediatype = 'Blog'
Any advice?
EDIT:
Here is the table with:
There is more columns but these are ones I want to focus on.

Answer 1

Your generate SQL request seems to have a syntax error. Just change the way you generate it.
Instead of
foreach($columns as $val)
$query .= "$val, ";
Try
$query .= implode(', ' $columns);
That will skip the last comma.

Answer 2

The blog column had an extra empty line that 'Blog%' wasn't working on. I went in the database and deleted the extra line and used the query again and it worked.
Thanks everyone for the help :)