Storing multiple input values in single field in database and retrieving separately

Questions first:

• Where does $Username variable coming from?

• Do you really intend to store an array to your users.UserData column?

If you want to continue this schema of yours, you have to figure out how to store them to your database. You will encounter an error if you try to use *_real_escape_string() if you use it in an array. Second parameter will be looking for strings, not for an array.

You can try to run them all and then use *_real_escape_string and then restore them.

for($x = 0; $x < count($_POST["UserData"]); $x++){

  $data[$x] = mysqli_real_escape_string($con, $data[$x]);

}

Did you properly concatenate the variable to your HTML form?

echo '<form action="edit.php" method="POST" id="content">
          <h3>Homepage</h3>
          <hr/>
          <h4>Title: </h4><input type="text" name="UserData[]" value="'.$UserData[0].'"><br/>
          <h4>Subtitle: </h4><input type="text" name="UserData[]" value="'.$UserData[1].'"><br/>
          <h4>Footer: </h4><input type="text" name="UserData[]" value="'.$UserData[2].'"><br/>
          <input type="submit" value="Save" name="datasave" id="save">
     </form>';

@ChrisBaker covers the rest of storing and retrieving the data from your database.

Standard way of storing Data

But the advisable way to store such data in your database is to restructure your table in your database. Separate each into their own column:

Your users table will look like:

id |  Username   |   title   | subtitle  | footer  |
---+-------------+-----------+-----------+---------+
 1 | LankyMoose  |    OP     |  English  | sticky  |
 2 | Chris Baker | Boy Scout |  English  | dynamic |
 3 | Logan Wayne |   Whiner  |   Multi   |  none   |

So you can store them to your database and fetch them easier.

Dynamic Storing of Data

But what if those fields are dynamic? You want to store more data from the user (that is what I thought of when you try to insert an array of data from the user).

You can create extra tables that stores the different types of data from the user and stores the user's input. Lets name the first table for example, data_table:

 data_id | data_type
---------+-----------
    1    |   Title
    2    |   Subtitle
    3    |   Footer

Then for the second table which stores the users input, lets name it data_input:

input_id | data_id | user_id | user_input
---------+---------+---------+------------
    1    |    1    |    1    |     OP
    2    |    2    |    1    |   English
    3    |    3    |    1    |    sticky
    4    |    1    |    2    |  Boy Scout
    5    |    2    |    2    |   English
    6    |    3    |    2    |   dynamic
    7    |    1    |    3    |   Whiner
    8    |    2    |    3    |   Multi
    9    |    3    |    3    |    none

Your users table would look like this now:

user_id |   username    
--------+-------------
   1    |  LankyMoose
   2    |  Chris Baker
   3    |  Logan Wayne

So for example, you want to get data from LankyMoose, you can try this query:

SELECT a.username,
       c.data_type,
       b.user_input
FROM users a
     LEFT JOIN data_input b ON a.user_id = b.user_id
     LEFT JOIN data_table c ON b.data_id = c.data_id
WHERE user_id = 1

Result will be:

  username  | data_type | user_input
------------+-----------+------------
 LankyMoose |   Title   |    OP
 LankyMoose |  Subtitle |  English
 LankyMoose |   Footer  |   sticky

With this method, you can add more fields just by inserting data to data_table.

I would also suggest that you use prepared statement since you are already using mysqli_* extension.