preg_match('/^1\d{10,10}$/', $number)
  • And if it is even more precise, then from where it should begin, and then 10 digits it seems understandable - Vitaly
  • Unit + 10 digits? - Andrei NOP

2 answers 2

American. 11 digits in a row without a plus, starts with 1.

PS: http://www.hella.ru/code/codeworld.htm

    This regular expression matches a string of exactly 11 characters in length, the first of which is '1' , and the remaining ten are any numbers.

    Check