form validation

[vang163]

hi,

 

i'm currently stuck in validating some textfields in a html form using php.

I want to make the textfield to accept only characters that are pre-defined.

 

eg. textfield to accept only these defined alphabets/numbers/special characters: a-z,A-Z,0-9,!@#$%^&*()[]/\{}<>,.?;:"'

 

I've searched the web for solutions but no results, maybe i search with a wrong topic.

 

Can you show me how this can be done? your help is greatly appreciated, thanks.

[ron8000]

use a regular expression on the field input to match against a pattern full of the chars you want to allow.

 

$reg_exp = '/^[A-Za-z0-9\,\!\@\#\$\%\^&\*\(\)\[\]\/\\\{\}\<\>\,\.\?\;\:\"\']{,}$/'

if(preg_match($reg_exp, $field_text)
{
     echo "YAY we found a match!";
}
else
{
     echo "Try again!";
}

 

I do think that would do the trick for you. And you can find some great Regular Expression information at:

 

http://www.php.net/manual/en/book.pcre.php

http://www.regular-expressions.info/php.html

 

Hope this helps!

-Ron

[bluejay002]

if you want to screen the users' input from the client-side, meaning allowing the users to only type those characters you mentioned then you need to use JavaScript for that instead of PHP. I have been using that one also.

 

But still you need to screen that one the second time around it goes to the server, just in case those were bypassed. To do that, you need to use preg_match() to check if there are invalid characters for that and thus, you will use regex for that.

 

my two cents,

 

Jay

[vang163]

hi,

 

i've modify your code like below:

 

$regular_expression = '/^[A-Za-z0-9]/';    // to allow only A-Z, a-z, 0-9

 

if(!preg_match($regular_expression, $text_field_name))

{ $errors[] = 'Please remove special characters in the text field';

}

 

when i enter the following data into the textfield:

input 1:  !@#password

result: everything works fine, display error message

input 2: password!@#

result: error! it does not catch the special characters in the textfield and no display of error message

 

may i know where i have done wrong?

[ron8000]

<?php
$reg_exp = '/^[A-Za-z0-9\,\!\@\#\$\%\^&\*\(\)\[\]\/\\\{\}\<\>\,\.\?\;\:\"\']{,}$/';
?>

 

Note the ^ and & in the expression

 

the ^ will define the begin

 

the $ will define the end

 

so if you change your code to

 

<?php
$regular_expression = '/^[A-Za-z0-9]{,}$/'; 
?>

 

That should work for you.

 

-Ron

 

[vang163]

hi ron,

 

many thanks for your guidance. i've again modify your code like below:

 

$regular_expression = '/^[A-Za-z0-9]{,}$/';    // to allow only A-Z, a-z, 0-9 in text field

 

if(!preg_match($regular_expression, $text_field_name))

{  $errors[] = 'Please remove special characters in the text field';

}

 

But now all my acceptable data i enter into the textfield will give me this error message, except empty field will not give me this error message!

My acceptable data includes:

a. data in number

b. data in alphabet

c. data in alphabet and number

 

may i know where have gone wrong?

[ron8000]

Sorry about that it's the {,} i never used it empty like that and yes it does not work.

 

<?php

$reg_exp = '/^[a-zA-Z0-9 ]*$/';

?>
[\code]

notice the space in the [ ] and the *

the space in the [ ] will allow for a white space char if you do not want any white space, remove it and it will not match if there is a space char.

The * allows for 0 or more of the [ ] items.

Sorry for the crazyness, but I strongly suggest that you read up and have at least a basic understanding of Regular Expressions. They can be extreamly useful!

[vang163]

hi ron,

 

i've get the code working.

many thanks for your prompt reply, patience and guidance.