Beginner question: detecting specified character in string

[Julia Briggs]

Hello, trying to create logic tests against a string allowing someone
to enter a certain character once or twice into a form consecutively,
but not twice seperated between other characters....

so,

hello##there (ok)
hello#there (ok)
#hello#there (no)
##hello#there (no)
###hellothere (no)

How would I do this? I was looking at strstr and some others, but not
sure. I have many challenges like this ahead, so hopefully someone
building this will help my mind figure out other designs.

Thanks so much!

-Julie

[Julia Briggs]

wanted to add a little depth to the above, this is what i'm trying to
incorporate the above logic into:

(This so far will only accept upper and lower case letters)

if(ereg("[^a-zA-Z]", $string)){

[some error message]

} else {

[$string passes validation....]

}

....so, confirming, I am trying to allow percisely # or ##, nothing
more. confirming ## can't be two or more #'s split up, two #'s only.
(or one) :)

[John Dunlop]

Julia Briggs wrote:

Hello, trying to create logic tests against a string allowing someone
to enter a certain character once or twice into a form consecutively,
but not twice seperated between other characters....

so,

hello##there (ok)
hello#there (ok)
#hello#there (no)
##hello#there (no)
###hellothere (no)

preg_match('`^[^#]*#{0,2}[^#]*$`',$subject)

Explanation: The pattern matches zero or more of any
character except '#', then zero, one or two '#'s, then zero
or more of any character except '#' again.

Have a good weekend!

--
Jock

[Julia Briggs]

Thanks a million. So I can see how it delineates in the mix, how would
I add into that preg_match the following:

1) Allow all A-Z and a-z characters, with no special characters except
a period and apostrophe
2) Allow all numbers

Could you show this as two examples, one with and without the numbers
matching?

[John Dunlop]

Julia Briggs wrote:

So I can see how it delineates in the mix, how would
I add into that preg_match the following:
I don't follow. What do you mean by 'add into'?
1) Allow all A-Z and a-z characters, with no special characters except
a period and apostrophe
Together those characters form the character class [a-zA-
Z.']. Do you want to substitute that for the '#' in the
previous pattern? If so, then:

`^[^a-zA-Z.']*[a-zA-Z.']{0,2}[^a-zA-Z.']*$`

Explanation: match zero or more characters except any from
your character class (a-z, A-Z, full stop and apostrophe);
then match zero, one or two characters from your character
class; then, finally, match zero or more characters except
any from your character class.

Or do you mean something else?
2) Allow all numbers

For decimal numbers just add \d or [0-9]; e.g.,

`^[^a-zA-Z\d.']*[a-zA-Z\d.']{0,2}[^a-zA-Z\d.']*$`

You must escape all the single-quotes if the pattern string
is single-quoted.

Slainte!

--
Jock

[Julia Briggs]

Sorry, for clarification, I meant introduce by "add". I want to keep
the # and its original expression, and also allow all
uppercase/lowercase and a period and apostrophe.

Sincerely,

Julia

John Dunlop wrote:

Julia Briggs wrote:

So I can see how it delineates in the mix, how would
I add into that preg_match the following:

I don't follow. What do you mean by 'add into'?

1) Allow all A-Z and a-z characters, with no special characters except a period and apostrophe

Together those characters form the character class [a-zA-
Z.']. Do you want to substitute that for the '#' in the
previous pattern? If so, then:

`^[^a-zA-Z.']*[a-zA-Z.']{0,2}[^a-zA-Z.']*$`

Explanation: match zero or more characters except any from
your character class (a-z, A-Z, full stop and apostrophe);
then match zero, one or two characters from your character
class; then, finally, match zero or more characters except
any from your character class.

Or do you mean something else?

2) Allow all numbers

For decimal numbers just add \d or [0-9]; e.g.,

`^[^a-zA-Z\d.']*[a-zA-Z\d.']{0,2}[^a-zA-Z\d.']*$`

You must escape all the single-quotes if the pattern string
is single-quoted.

Slainte!

--
Jock

[John Dunlop]

Julia Briggs wrote:

I want to keep the # and its original expression, and also
allow all uppercase/lowercase and a period and apostrophe.

The original pattern did that.

But if you want to match only a-z, A-Z, full stops and
apostrophes, and an optional number sign ('#') appearing
once or twice together -- in other words, the original
pattern but with the characters other than the number sign
restricted to the set [a-zA-Z.'] -- then

`^[a-zA-Z.']*#{0,2}[a-zA-Z.']*$`

Is that what you're after?

--
Jock

[Julia Briggs]

Correct criteria, but blows up on execution with my code. :/ - I think
it is because of the introduced ' symbol. Does that need to be
escaped, or something else? I took it out and it works. This will not
permit spaces. I need those. One more small detail, I would love it
if it could work this way -- to have all of this criteria as we have it
(plus spaces) and only allow one instance of a period/full stop too.

Here is what I have codewise so far that is blowing up because of the '

if(preg_match('`^[a-zA-Z.']*-{0,2}[a-zA-Z.']*$`',$string)) { [etc...]

Thank you from the bottom of my heart for this. You extended
explanations are great. Very professional, helpful and first class
John.

Sincerely,

Julia.

John Dunlop wrote:

Julia Briggs wrote:

I want to keep the # and its original expression, and also
allow all uppercase/lowercase and a period and apostrophe.

The original pattern did that.

But if you want to match only a-z, A-Z, full stops and
apostrophes, and an optional number sign ('#') appearing
once or twice together -- in other words, the original
pattern but with the characters other than the number sign
restricted to the set [a-zA-Z.'] -- then

`^[a-zA-Z.']*#{0,2}[a-zA-Z.']*$`

Is that what you're after?

--
Jock

[John Dunlop]

Julia Briggs wrote:

Correct criteria, but blows up on execution with my code. :/ - I think
it is because of the introduced ' symbol. Does that need to be
escaped, or something else? I took it out and it works.
If the pattern string is enclosed in single-quotes, then,
yes, single-quotes in the pattern itself must be escaped so
that they're not interpreted as closing the string. You
would typically escape them with backslashes.
This will not permit spaces. I need those.
Simply change your pattern to

`^[a-zA-Z.' ]*#{0,2}[a-zA-Z.' ]*$`

(with single-quotes escaped if required)
One more small detail, I would love it if it could work this way -- to
have all of this criteria as we have it (plus spaces) and only allow one
instance of a period/full stop too.
I can't think how to do that in the same pattern. You could
split it into two patterns, with the one most likely to fail
coming first. Or you could use the string functions.

http://www.php.net/manual/en/ref.strings.php
Here is what I have codewise so far that is blowing up because of the '

if(preg_match('`^[a-zA-Z.']*-{0,2}[a-zA-Z.']*$`',$string)) { [etc...]

Change your expression to

if(
preg_match(
'`^[a-zA-Z.\' ]*-{0,2}[a-zA-Z.\' ]*$`',
$string)
&&
substr_count($string,'.')<2)

There is an additional expression which evaluates to true
only if there are fewer than two full stops in $string.

http://www.php.net/manual/en/function.substr-count.php

Have a relaxing Sunday.

--
Jock