Constant	Description
Anchored	If this compilation is specified, the pattern is forced to be "anchored", that is, it is constrained to match only at the first matching point in the string that is being searched (the "subject string").
Caseless	Specifies a case-insensitive match.
DollarEndOnly	Specifies that the dollar ($) expression will not match a newline at the end of the subject string, but only the actual end of the string. By default, a dollar will match the end of the string with or without a newline preceding it.
DotAll	Specifies that the dot (.) regular expression will even match line endings, allowing you to treat a multi-line subject text as one long line.
Extended	Specifies extended regular-expression syntax. In this mode, whitespace and comments are allowed in your regular expressions. Comments are Perl-style, that is, they start with a hash (#) and continue until the next newline.
Extra	This compilation option was invented in order to turn on additional functionality of PCRE that is incompatible with Perl, but it is currently of very little use.
Greedy	Constant that allows to remove the ungreedy default option of Replace.
MultiLine	Specifies that the subject text is multi-line, so that the caret (^) and dollar ($) modifiers will match the beginnings and endings of lines anywhere within the text.
NoAutoCapture	If this compilation option is specified, it disables the use of numbered capturing parentheses in the pattern.
UTF8	This option causes PCRE to regard both the pattern and the subject as strings of UTF-8 characters instead of single-byte character strings. However, it is available only when PCRE is built to include UTF-8 support. If not, the use of this option provokes an error.
Ungreedy	Inverts the greediness of each quantifier. Every quantifier has a greedy and an ungreedy variant, e.g. the "+" quantifier is greedy and its ungreedy variant is "+?". Setting the Ungreedy flag converts all greedy variants to ungreedy ones and vice versa. It does not make all quantifiers ungreedy.