PHP regex to remove multiple ?-marks

Question

I'm having trouble coming up with the correct regex string to remove a sequence of multiple ? characters. I want to replace more than one sequential ? with a single ?, but which characters to escape...is escaping me.

Example input:

Is this thing on??? or what???

Desired output:

Is this thing on? or what?

I'm using preg_replace() in PHP.

Answer 1

preg_replace('{\?+}', '?', 'Is this thing on??? or what???');

That is, you only have to escape the question mark, the plus in "\?+" means that we're replacing every instance with one or more characters, though I suspect "\?{2,}" might be even better and more efficient (replacing every instance with two or more question mark characters.