Question

how do I write an expression which checks for lowcaps, dots, and without any white space in the string?

the code below so far was trying to check for lowcaps and dots (it does not work anyway!) but I don’t know how to add in the expression for white spaces.

# check for matches of lowcaps or lowcaps with a dot
if (!preg_match('/([a-z0-9]|[a-z0-9\.])/', $cst_value))
{
  $error = true;
  echo ' please use lowcaps only with dot(s) and without any spacing.';
}

Answer 1

[a-z0-9.] matches a lower-case letter or a digit or a dot.
[^a-z0-9.] matches all characters that are not a lower-case letter or a digit or a dot.
So if /[^a-z0-9.]/ matches anywhere the string contains something other than lc-letter,digit or dot. If it does not match your condition is fulfilled.

if ( !preg_match('/[^a-z0-9.]/', $cst_value) ) {
  // only lower-case letters, digits or dots
}

or without digits

if ( !preg_match('/[^a-z.]/', $cst_value) ) {
  // only lower-case letters or dots
}

---

update: example:

foreach( array('abcdef', 'abc de', 'abc.de', 'aBcde') as $cst_value) {
  echo $cst_value, ': ';
  if ( !preg_match('/[^a-z.]/', $cst_value) ) {
    echo " ok.\n";
  }
  else {
    echo "failure\n";
  }
}

prints

abcdef:  ok.
abc de: failure
abc.de:  ok.
aBcde: failure