This is the pattern modifier for the regular expression.
(? i) is not case-sensitive when matched. Indicates that the match is case-insensitive.
(? s) is Singleline (single-line mode). Represents the meaning of a change, which matches each character (including the newline character \ n).
(? m) is the multiline (multiline mode). Represents changing the meaning of ^ and $ so that they match at the beginning and end of any line, not just at the beginning and ending of the entire string. (In this mode, the exact meaning of $ is to match the previous position and the position before the end of the string.)
(? x): Indicates that if the modifier is added, the white space character in the expression will be ignored unless it has been escaped.
(? e): Indicates that this modifier is only useful for replacement and represents the PHP code in replacement.
(? A): Indicates that if this modifier is used, the expression must be the beginning of the matching string. For example, "/a/a" matches "ABCD".
(? E): In contrast to "M", means that if this modifier is used, "$" matches the end of an absolute string, rather than a newline character, which is turned on by default.
(? U): The expression is similar to the question mark and is used to set "greedy mode".
?: （。 A single question mark is not capture mode
Written as: (?:)
How to turn off the ability to capture parentheses.
And just use it to group, by adding the following in the left parenthesis:?
The first round bracket here is used for grouping only, not capturing variables.
"(?:\ \w+\\s (\\w+)) "
