Question

I have big string in that I need to check if number is present which is more than 3.
Means “some string2” will be invalid , but “some string 3″,”some string7” will be correct.

Answer 1

preg_match('/some\s*string\s*([3-9][0-9]*|[1-9][0-9]+)/i', $haystack);

And here the working example

But, after examining your use-case, which seems to be checking for a specific version in an application description, I too would advise you to just get the number out of the string and compare it to an actual number to be sure it’s larger or equal than 3:

preg_match('/([0-9]+)/', $string, $matches);
if ($matches[1] >= 3) {
  // Do something
}