[Solved] How to identify, if a string contains numbers?

Hi

Say there are billion strings like:

$string1 = 'AD 123456 d 265 SFreg'

$string2= '3255'

$string3 = 'AAA 87654321 reggw 234 sr EE#!¤ '

etc..

I wold like to filter out numbers from the strings. But the sequence must contain at least 5 numbers in a row. Is it possible to do so?

From this example only $string1 and $string3 are good & output should be

12345

and

87654

Is there a way to identify numbers in the string ?