Regular (? I, m, S, X, g)

 

Regular I, S, M, G

These are pattern delimiters -- describe the delimiters used in regular expression pattern.

I
If this modifier is set, characters in the mode match both uppercase and lowercase letters.

M
When this modifier is set, "row start" and "Row end" not only match the start and end of the entire string, but also match the end and end of the linefeed respectively.

S
If this modifier is set, the dot metacharacters (.) In the pattern match all characters, including line breaks. If this parameter is not set, line breaks are not included.

X
If this modifier is set, the white space characters in the mode are ignored except for escaped characters or in the character class, all the characters between the # And the next line break except the unescaped character class, including both ends, are ignored.

E
If this modifier is set, preg_replace () replaces the reverse reference in the replacement string normally,