Taking only letters out of string is not working in PHP

I have a database table which contains some application numbers. I want to take only letters out of its for example, I did the following:

$post_content="BGCG0";
$only_text =preg_replace("/[^a-zA-Z0-9]+/", "", $post_content);
echo $only_text;

However it doesn’t do it. Can anyone please tell me how to accomplish this?

>Solution :

You’re allowing digits in your regex. Remove the 0-9 part from it and you should be OK:

$only_text = preg_replace("/[^a-zA-Z]+/", "", $post_content);
# Here -----------------------------^