Remove specific characters at beginning and end of string

问题

I am using PHP and I am trying to remove all underscore characters from the end and beginning of a string.

Here's the string: ____a_b_c__________
And I want the result to be: a_b_c

I have tried with this regular expression but it's not working:

preg_replace('/[^a-z]+\Z/i', '', '____a_b_c__________');

回答1:

Why not just use trim:

$string = trim($string, '_');

Regex is for pattern matching ___ is not a pattern it's just underlines.

But if I was gonna use a Regex, I'd do something like this:

$string = preg_replace('/^_+|_+$/', '', $string);

For the regular expression

• ^ is the start of a line
• _ is underline, the + is one or more
• | is OR
• _ is underline, the + is one or more
• $ is the end of line

Then we just replace it with ''

来源：https://stackoverflow.com/questions/49724039/remove-specific-characters-at-beginning-and-end-of-string