$re = '/(?ix)
(\d+:\d\d)
\s+
.*?
\b
(
mon(?:d(?:ay?)?)
|tue(?:s(?:d(?:ay?)?)?)?
|wed(?:n(?:e(?:s(?:d(?:ay?)?)?)?)?)?
|thu(?:r(?:s(?:d(?:ay?)?)?)?)?
|fri(?:d(?:ay?)?)
|sat(?:u(?:r(?:d(?:a)?)?)?)?(?:y)?
|sun(?:d(?:ay?)?)
)
.*/m';
$str = '0:18 on Tuesday\'s mini
1:43 Wednesday. dang!
2:01 this Sat 😎';
$subst = "$1 $2";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php