Mobile number validation pattern in PHP

Question

I am unable to accurately write the 10-digit mobile number pattern in PHP (1234567890 formats). Email verification is operational.

My code:

function validate_email($email)
{
return eregi("^[_\.0-9a-zA-Z-]+@([0-9a-zA-Z][0-9a-zA-Z-]+\.)+[a-zA-Z]    {2,6}$", $email);
}

function validate_mobile($mobile)
{
  return eregi("/^[0-9]*$/", $mobile);
}

Can someone please help me with this?