php script to retrieve enum values from sql table

I have an sql table with multiple fields and 4 of them are enums. I wrote a script that runs thought the table and retrieve the enums and put them in a 2 dimension array.

Unfortunately this script is extreamly slow and I can't fix it.

<?php

require_once('mySQL_Connect.php');

$con = ConnectToDataBase();
if ($con == false)
{
    //data returned will be null
    exit;
}

$db = 'courses_db';
$table = 'courses';

$fields = array(
'training_field',
'speciality_field',
'type',
'language');

$enums = array();

foreach ($fields as $colomn) {
$sq1 = "SELECT 
            column_type 
        FROM 
            information_schema.columns 
        WHERE 
            table_schema = '$db' 
        AND 
            table_name = '$table'
        AND 
            column_name = '$colomn'";
$query =  mysqli_query($con,$sq1);

$stack = array();   
$i = 0;
$stack[$i]=$colomn;
if ($fetch = mysqli_fetch_assoc($query) )
{
    $enum = $fetch['column_type'];
    $off = strpos($enum,"(");
    $enum = substr($enum, $off+1, strlen($enum)-$off-2);
    $values = explode(",",$enum);

    // For each value in the array, remove the leading and trailing
    // single quotes, convert two single quotes to one. Put the result
    // back in the array in the same form as CodeCharge needs.

    for( $n = 0; $n < Count($values); $n++) {
    $val = substr( $values[$n], 1,strlen($values[$n])-2);
    $val = str_replace("''","'",$val);
    $stack[$i+1]=$val;
    $i++;
    }
}
    // return the values array to the caller
    //echo json_encode( $stack);
    array_push($enums,$stack);
    reset($stack);
}
echo json_encode($enums);
?>