正则表达式查找除x，a，n， - 之外的所有字符

Question

This is my first post here. I've started writing a few and always managed to figure it out on my own. Alas, regular expressions make me want to beat my face on the street and I'm stuck.

I'm trying to write a regular expression that will check a string for any character that isn't an x, a, n, or -. Here's what I have:

    preg_replace( '/^[^xan\-]+$/' , 'x' , $this->str_key_mask )

I'm sure it's something simple, but I've tried adding, changing, and removing metacharacters and can't get the result I want.

For instance, if I pass in xan-nax-jxy, I want to get back xan-nax-xxx due replacing the j and y with x. If I pass in xxx-aaa-nnn, it should return xxx-aaa-nnn since nothing needs replacing.

Answer 1

With the ^ and $ anchors, you will only match strings that are composed of entirely characters that are not x, a, n, or -. Since you want to match each of those characters separately and replace each one with 'x', just remove the anchors and the repetition:

preg_replace( '/[^xan\-]/' , 'x' , $this->str_key_mask )

Removing the repetition is necessary if you want a string like 'jy' to become 'xx'. If instead you want 'jy' to become 'x', keep the + after your character class so that consecutive characters are replaced together.