$re = '/(?i)VITA?MIN\s*C##.*?##[0-9]+ days/i';
$str = '1. As VITMINC##1-0-1##1 days.As
2. amlodipine ##vitamin c##diclo##tabramycin eye drop##metformin##0-0-1##15 days. amlodipine ##1-0-1## 3 days.
3. Xylometazoline(P) Nasal drops##0-1-0##2 days. Paracetamol 500mg tab##0.5-0-0-0##2 days. VITMINC##0.5-0-0##2 days. Chlorpheniramine maleate 4mg tab##0-1-0##2 days.
4. VITMINC##0-0-0-1##2 days.
5. amlodipine##vitamin c##diclo##tabramycin eye drop##metformin##0-0-1##15 days.';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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