PHP/mySQL get all column names and create list - php

Question

I'm using this to define the valid keys that can be used to perform a search on my front end:
$validKeys = array('gender','marital_status', 'age');
The rest of my code works great in that it only accepts keys sent to it in an AJAX call that are in this array.
However, I want to be able to make this list ('gender','marital_status', 'age') dynamic. That is, I'd like to include all of the columns from my table in here so that every column is essentially a valid key. I have about 10-15 depending on the table and I'd rather not hard-code it into each PHP file.
How would I go about getting all the column names in my table and arranging them into this variable? So, I need to get all the names, put them in single quotes and comma separate. Unless there's a way to get them in a proper array and skip the array part of defining the $validkeys variable.
If I var_dump $validKeys, I get this:
array(5) {
[0]=>
string(6) "gender"
[1]=>
string(14) "marital_status"
[2]=>
string(3) "age"
[3]=>
string(7) "anglers"
[4]=>
string(8) "baseball"
}
Any direction would be appreciated.
EDIT: Should have been more explicit that I am using PDO.

Answer 1

you can try with mysqli's fetch_fields-function.
$finfo = $result->fetch_fields();
Documentation: http://php.net/manual/de/mysqli-result.fetch-fields.php

Answer 2

Run a query using the DESCRIBE syntax. That will return all columns to you which you can then place in the array.
DESCRIBE `table_name`;
Another option is SHOW COLUMNS. Either will work for your requirements.

Answer 3

I should have been a bit more explicit that I am using PDO, so Jay's answer above pointed me in the right direction and I found this answer that gave me the details: https://stackoverflow.com/a/7091984/989722
The full code snippet based on my question looks like this:
$q = $dbh->prepare("DESCRIBE full_db2");
$q->execute();
$table_fields = $q->fetchAll(PDO::FETCH_COLUMN);
$validKeys = $table_fields;