$phone = '000-0000-0000';

​

if(preg_match("/^[0-9]{3}-[0-9]{4}-[0-9]{4}$/", $phone)) {

  // $phone is valid

}

   function isDigits(string $s, int $minDigits = 9, int $maxDigits = 14): bool {

        return preg_match('/^[0-9]{'.$minDigits.','.$maxDigits.'}\z/', $s);

    }

​

    function isValidTelephoneNumber(string $telephone, int $minDigits = 9, int $maxDigits = 14): bool {

        if (preg_match('/^[+][0-9]/', $telephone)) { //is the first character + followed by a digit

            $count = 1;

            $telephone = str_replace(['+'], '', $telephone, $count); //remove +

        }

​

        //remove white space, dots, hyphens and brackets

        $telephone = str_replace([' ', '.', '-', '(', ')'], '', $telephone);

​

        //are we left with digits only?

        return $this->isDigits($telephone, $minDigits, $maxDigits);

    }

​

    function normalizeTelephoneNumber(string $telephone): string {

        //remove white space, dots, hyphens and brackets

        $telephone = str_replace([' ', '.', '-', '(', ')'], '', $telephone);

        return $telephone;

    }

​

// how to use 

$tel = '+9112 345 6789';

if (isValidTelephoneNumber($tel)) {

    //normalize telephone number if needed

echo normalizeTelephoneNumber($tel); //+91123456789

}

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