PHP Regular Expression modifiers

Preg_match_all ("/(. +) <\/form>/isu", $string, $result);

3 modifiers are added here/behind
I is a case-insensitive match
S is a match with a newline
U is a non-greedy mode. Match the least part.

Modifier:
I: If you add "I" to the modifier, the regular will remove the case sensitivity, i.e. "a" and "a" are the same.
M: Default regular start "^" and end "$" just for regular strings if you add "M" to the modifier, then the start and end will refer to each line of the string: the beginning of each line is "^" and the End is "$".
S: If "s" is added to the modifier, then the default "." Any character that represents anything other than a newline character will become any characters, including line breaks!
x: If the modifier is added, the white space character in the expression will be ignored unless it has been escaped.
E: This modifier is only useful for replacement, and represents the PHP code in replacement.
A: If you use this modifier, the expression must be the beginning of the matching string. For example, "/a/a" matches "ABCD".
E: In contrast to "M", if this modifier is used, then "$" will match the end of the absolute string, not the line break, which is turned on by default.
U: Similar to question mark, used to set "greedy mode".
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For more explanations, please refer to: http://php.net/manual/zh/reference.pcre.pattern.modifiers.php

PHP Regular Expression modifiers