- var_dump: documentation ( source)
- preg_match_all: documentation ( source)
<?php
$pattern = <<<'PATTERN'
/(?xJ)
(?<DN>Mon|Fri|Sun)(?:day)?|
(?<DN>Tue)(?:sday)?|
(?<DN>Wed)(?:nesday)?|
(?<DN>Thu)(?:rsday)?|
(?<DN>Sat)(?:urday)?
/
PATTERN;
$subject = "Monday\nThursday";
preg_match_all($pattern, $subject, $matches, PREG_PATTERN_ORDER);
var_dump($matches);