PHP preg_match only letters and no numbers, maybe an explanation

Question

I have this email regex, and i would like to make same thing with a name regex, so you can't write numbers in a name, how should i change it?

if (!preg_match("/^[[:alnum:]][a-z0-9_.-]*@[a-z0-9.-]+\.[a-z]{2,4}$/i", trim($_POST['email']))) {
    $emailError = 'You entered an invalid email address.';
    $hasError = true;
}

I know that [a-z0-9_.-] means that a-z 0-9 and _ . - is usable. But i want to only use a-z and this is why my brain is breaking across, as i don't understand the whole sentence, could anyone "translate" it to only use a-z and no numbers neither _ - .? I would like it to be changed to a name regex, so people can't write numbers in their name.

I understand that i can write

if (!preg_match("/^[[:alnum:]][a-z]*@[a-z]+\.[a-z]{2,4}$/i", trim($_POST['name']))) {
    $nameError = 'You entered invalid characters in your name.';
    $hasError = true;
}

but for me it doesn't make any sense, how i should enter that into the regex above.

but i could also type in this? so i say if it contains 0-9 then its invalid? but i don't know what it means all these characters in the sentence.

if (preg_match("/^[[:alnum:]][0-9]*@[0-9]+\.[0-9]{2,4}$/i", trim($_POST['name']))) {
    $nameError = 'You entered invalid characters in your name.';
    $hasError = true;
}

I tried to research about "preg_match" but i can't find an explanation, so i can make my a regex for "preg_match" on my own

"Only alphanumeric and no numbers"? You know alphanumeric includes numbers, right? (Also, consider that people may have spaces, apostrophes, accented characters, hyphens, and perhaps other things I haven't thought of in their name...) — Matt Gibson, Dec 13 '14 at 15:09

Avinash Raj · Answer 1 · 2014-12-14T08:28:23.530

1

You could try the below.

/^[a-z]+@[a-z]+\.[a-z]{2,4}$/i

[[:alnum:]] Matches both alphabets and numbers but POSIX [[:alpha:]] matches only the alphabets.
[a-z]* zero or more lowercase letters. [a-z]+ one or more lowercase letters.
i modifier helps to do a case insensitive match.

edited Dec 14 '14 at 08:28

answered Dec 13 '14 at 14:48

Avinash Raj

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I would get rid of the `[[:alpha:]]`, nobody has an accented first letter of their name, I don't see any logic in putting that there. – pguardiario Dec 14 '14 at 07:02
you mean, i need to change `[[:alpha:]]` to `[a-zA-Z]` ? – Avinash Raj Dec 14 '14 at 07:03
I meant change `[[:alpha:]][a-z]*` to `[a-z]+` – pguardiario Dec 14 '14 at 07:05
That's an good idea, but what if op wants to allow capital capital letter at the first , like `Foo@bar.com` ? I need to change alpha to `[[:alpha:]]+` – Avinash Raj Dec 14 '14 at 07:07
`[[:alpha:]]` means `a-z` plus the (latin) accented letters. Case insensitive is covered by the `//i` – pguardiario Dec 14 '14 at 07:55
So you mean i should try do this? preg_match("/^[a-z]+@[a-z]+\.[a-z]{2,4}$/i" – Zeuthenjr Dec 15 '14 at 12:42

score 0 · Answer 2 · answered Dec 13 '14 at 15:12

0

If you want to understand the regex pattern try using http://regex101.com . That will let you analyze each part of the pattern.

You can try using this, it should do the job:

/^[[:alpha:]][a-z]*@[a-z]+\.[a-z]{2,4}$/i

But the simpler regex for a name check that I use and haven't had any issues with is:

/^([a-z])+$/i

Although the first one may be better (?) the second one makes the regex slightly more understandable in my opinion.

answered Dec 13 '14 at 15:12

Myles Offord

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I don't think this captures what you expect it to capture. – pguardiario Dec 14 '14 at 07:04

PHP preg_match only letters and no numbers, maybe an explanation

2 Answers2