PCRE Modifiers
Modifiers are appended after the closing delimiter. Common ones: i (case-insensitive), m (multiline), s (dot matches newline), x (extended/verbose), u (UTF-8).
PHP
Intermediate
5 min read
PHP Regex Modifiers
Example
<?php
// i: case-insensitive
preg_match("/hello/i", "Hello World"); // matches
// m: ^ and $ match line boundaries
preg_match_all("/^\w+/m", "line1
line2
line3", $m);
// $m[0] = ["line1", "line2", "line3"]
// s: dot matches newline
preg_match("/start.*end/s", "start
middle
end");
// x: extended/verbose mode — whitespace and # comments ignored
$pattern = "/
^ # Start of string
(\d{4}) # 4-digit year
- # Separator
(\d{2}) # 2-digit month
- # Separator
(\d{2}) # 2-digit day
$ # End of string
/x"; Pro Tip
The /x modifier makes complex patterns readable by allowing whitespace and comments inside the regex literal.