根据子字符串删除字符串

Question

I want to remove substrings from a string. These substrings are always between whitespaces and contain either push or pull.

Let's say I have the following string:

col-md-4 col-sm-6 col-md-pull-6 col-sm-push-4

How would I get the following (using PHP preg_replace)?

col-md-4 col-sm-6

Answer 1

You can do it like this:

$result = preg_replace('~(?:\s*+\S*pu(?:ll|sh)\S*)+~', '', $str);

pattern details:

~                # pattern delimiter
(?:              # open a non capturing group
    \s*+         # zero or more whitespaces (possessive)
    \S*          # zero or more non-whitespaces
    pu(?:ll|sh)  # push or pull
    \S*
)+               # repeat the non capturing group (1 or more)
~

Note: if the string begins with "push" or "pull", this pattern may let a leading whitespace, in this case, use rtrim to remove it.

Depending how looks your string, this variant that unrools the loop (?:[^p\s]+|p+(?!u(?:ll|sh)))*+ (that replaces more explicitly \S*) may be more performant:

(?:\s*+[^p\s]*+(?:p+(?!u(?:ll|sh))[^p\s]*)*+pu(?:ll|sh)\S*)+

about possessive quantifiers and lookarounds