Cannot get wpdb data (Error in a simple fuction) [closed]

Question

I'm using Cryto Plugin and want to get coin price data from plugin db.

For easy practice, I'm trying to get BTC data.

<?php function get_coin_price($coin_symbol) {
  global $wpdb;

  $coin_price = $wpdb->get_var($wpdb->prepare("SELECT price FROM {$wpdb->prefix}cmc_coins_v2 WHERE symbol = '%s'", $coin_symbol));

  return $coin_price;
}?>

And if I want to get BTC price, I use this code.

<?php get_coin_price(BTC); ?>

However I'm getting this error
"Use of undefined constant BTC - assumed 'BTC' (this will throw an Error in a future version of PHP)"
Is there a problem in data type? or maybe am I not using $wpdb->get_var or wpdb->prepare correctly?

Answer 1

What about changing BTC to a string <?php get_coin_price('BTC'); ?>

Answer 2

should be a comment but can't.
your error just says that in <?php get_coin_price(BTC); ?> BTC is considered a variable but is not defined and compiler assume the variable as a string, it doesn't seems to crash your script, but still should be used like so <?php get_coin_price("BTC"); ?>