Php Regular Expression suffix

Perl-style Regular Expressions allow you to place a single character option (FLAG) behind the regular expression mode to modify the matching interpretation or behavior. For example, to perform case-insensitive matching, you can simply use the I flag:
Preg_match ('/cat/I', 'Stop, Catherine! '); // Returns true if returns is true.
Table 4-12 shows the modifiers from Perl supported in Perl-Compatible Regular Expressions:
Table 4-12: Perl flag

Modifier	Yi
/Regexp/I	Case-insensitive matching
/Regexp/s	Match a period (.) to any character, including a line break (\ n)
/Regexp/x	Remove blank spaces and comments from the Mode
/Regexp/m	Make ^ match the content after the line break (\ n), the dollar sign ($) matches the content before the line break (\ n)
/Regexp/e	If the replacement string is a PHP code, run eval () to obtain the actual replacement string.

PHP's Perl-Compatible Regular Expression functions also support other modifiers not supported in Perl, as shown in Table 4-13:
Table 4-13: Other PHP flags

Modifier	Yi
/Regexp/U	Reverse the greed of sub-models; * match as few as possible with + rather than as much as possible.
/Regexp/u	Treat pattern strings as UTF-8 Encoding
/Regexp/X	If a backslash is followed by a character with no special meaning, an error is generated.
/Regexp/	Position the anchor at the beginning of the string as if there is a ^ in the pattern.
/Regexp/D	Make $ match the end of only one line
/Regexp/S	Make the expression parser more careful to check the structure of the mode, so that the second Runtime (such as in a loop) speeds up