The following list contains all possible modifiers supported by the PCRE functions in PHP. Some Perl-specific modifiers are not supported, and conversely, there are some modifiers that Perl doesn’t have.
|i||When this modifier is used, the matching of alphabetic characters in the pattern becomes non-case-sensitive; for example, /sgi/i matches both sgi and SGI. This is equivalent to Perl’s /i modifier.|
|m||By default, PCRE treats the subject string as consisting of a single “line” of characters (even if it actually contains several newlines). The“start of line” metacharacter (^) matches only at the start of the string, while the “end of line” metacharacter ($) matches only at the end of the string, or before ...|