[RESOLVED] Simple regular express help!

alanzhao

Hi,

I need a regular expression to match a code name which only alphabet and underscore is allowed. but I tried the following statement, it doen't work,

if (!eregi("[_a-z]", $code)) $error = 'Invalid category code format! Only letters and underscores are allowed!';

Any ideals?

Thanks!

NogDog

if(eregi('[^_a-z]', $code))
{
  // invalid character was entered
}

alanzhao

Thanks!

it worked!

Can you explain the differences?

Thanks!

NogDog

Your way was saying, "if there is not an underscore or a letter somewhere in the string, then it is invalid," so it does not care if there are any invalid characters as long as there is at least one valid character. My way is saying, "if there is any character in the string that is not an underscore or a letter, then it is invalid". (The "^" immediately after the opening square bracket indicates negation in that character class.)

alanzhao

Got you.

Thanks!