PHP preg_match: any letter but no numbers (and symbols) - php

Question

I am trying to set a validation rule for a field in my form that checks that the input only contains letters.
At first I tried to make a function that returned true if there were no numbers in the string, for that I used preg_match:
function my_format($str)
{
return preg_match('/^([^0-9])$', $str);
}
It doesn't matter how many times I look at the php manual, it seems like I won't get to understand how to create the pattern I want. What's wrong with what I made?
But I'd like to extend the question: I want the input text to contain any letter but no numbers nor symbols, like question marks, exclamation marks, and all those you can imagine. BUT the letters I want are not only a-z, I want letters with all kinds of accents, as those used in Spanish, Portuguese, Swedish, Polish, Serbian, Islandic...
I guess this is no easy task and hard or impossible to do with preg_match. It there any library that covers my exact needs?

Answer 1

If you're using utf-8 encoded input, go for unicode regex. Using the u modifier.
This one would match a string that only consists of letters and any kind of whitespace/invisible separators:
preg_match('~^[\p{L}\p{Z}]+$~u', $str);

Answer 2

function my_format($str)
{
return preg_match('/^\p{L}+$/', $str);
}
Simpler than you think about!
\p{L} matches any kind of letter from any language

Answer 3

First of all,Merry Christmas.
You are on the right track with the first one, just missing a + to match one or more non-number characters:
preg_match('/^([^0-9]+)$/', $str);
As you can see, 0-9 is a range, from number 0 to 9. This applies to some other cases, like a-z or A-Z, the '-' is special and it indicates that it is a range. for 0-9, you can use shorthand of \d like:
preg_match('/^([^\d]+)$/', $str);
For symbols, if your list is punctuations . , " ' ? ! ; : # $ % & ( ) * + - / < > = # [ ] \ ^ _ { } | ~, there is a shorthand.
preg_match('/^([^[:punct:]]+)$/', $str);
Combined you get:
preg_match('/^([^[:punct:]\d]+)$/', $str);

Answer 4

Use the [:alpha:] POSIX expression.
function my_format($str) {
return preg_match('/[[:alpha:]]+/u', $str);
}
The extra [] turns the POSIX into a range modified by the + to match 1 or more alphabetical characters. As you can see, the :alpha: POSIX matches accented characters as well
If you want to include whitespace, just add \s to the range:
preg_match('/[[:alpha:]\s]+/u', $str);
EDIT: Sorry, I misread your question when I looked over it a second time and thought you wanted punctuation. I've taken it back out.