正则表达式删除特定字符

Question

I have been using the following regex to replace all punctuation in a string:

preg_replace('/[^\w\s]/', '', $tweet);

with \\w being shorthand for [a-zA-Z0-9_] and \\s is used to ommit spaces. I learned this wisdom here: Strip punctuation in an address field in PHP . But now, I need the regex to strip all characters except

a-z and A-Z
{ and }

So it should strip out all dots, commas, numbers etc. What is the correct regex for this?

Answer 1

preg_replace('/[^a-zA-Z{} ]/', '', $tweet);

FakeRainBrigand在评论中提出的可能更快的变体，谢谢：

preg_replace('/[^a-zA-Z{} ]+/', '', $tweet);

Answer 2

preg_replace('/[^a-z{}]/i', '', $tweet);