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PHP Form Field Data Validation Example/Tutorial



Written by:dimport
Published by:SAJChurchey
Published on:2003-06-21 07:19:46
Topic:PHP
Search OSI about PHP.More articles by dimport.
 viewed 45522 times send this article printer friendly

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This is a simple script to illustrate the of a function, field_validator(), which I modified from an original piece of code submitted on the devshed forums.

The field_validator() function is an extremely useful function for validating simple data that is returned to your PHP script from an HTML form. By using the function you can validate that the data a user enters on a form is of the correct type (i.e. email, string, digit, number, alpha, alphanumeric) and that it is of the
correct length (i.e. > min length).

The function is as follows:

function field_validator($field_descr, $field_data, $field_type, $min_length="", $max_length="", $field_required=1) {
    # array for storing error messages
    global $messages;
    
    # first, if no data and field is not required, just return now:
    if(!$field_data && !$field_required){ return; }
     # initialize a flag variable - used to flag whether data is valid or not
    $field_ok=false;
     # this is the regexp for email validation:
    $email_regexp="^([a-zA-Z0-9_-.]+)@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.)|"
    $email_regexp.="(([a-zA-Z0-9-]+.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(]?)$";
     # a hash array of "types of data" pointing to "regexps" used to validate the data:
    $data_types=array(
        "email"=>$email_regexp,
        "digit"=>"^[0-9]$",
        "number"=>"^[0-9]+$",
        "alpha"=>"^[a-zA-Z]+$",
        "alpha_space"=>"^[a-zA-Z ]+$",
        "alphanumeric"=>"^[a-zA-Z0-9]+$",
        "alphanumeric_space"=>"^[a-zA-Z0-9 ]+$",
        "string"=>""
    );
    
    # check for required fields
    if ($field_required && empty($field_data)) {
        $messages[] = "$field_descr is a required field.";
        return;
    }
    
    # if field type is a string, no need to check regexp:
    if ($field_type == "string") {
        $field_ok = true;
    } else {
        # Check the field data against the regexp pattern:
        $field_ok = ereg($data_types[$field_type], $field_data);
    }
    
    # if field data is bad, add message:
    if (!$field_ok) {
        $messages[] = "Please enter a valid $field_descr.";
        return;
    }
    
    # field data min length checking:
    if ($field_ok && $min_length) {
        if (strlen($field_data) $max_length) {
            $messages[] = "$field_descr is invalid, it should be less than $max_length characters.";
            return;
        }
    }
}


This article was originally written by munk

Did you like this article? There are hundreds more.

Comments:
Anonymous
2008-03-11 17:53:17
Looks like the script is missing the ; after $email_regexp="^([a-zA-Z0-9_-.]+)@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.)|"

Also, add a > in the max length comparison
if (strlen($field_data) > $max_length) {
Anonymous
2009-01-01 18:09:37
okay
Anonymous
2009-07-13 16:24:53
Great tutorial! I have added this to my new famous logos blog. You can see a list of famous company logo designs there too,
Anonymous
2010-01-20 07:37:58
12115
Anonymous
2010-02-12 19:41:41
fffff
Anonymous
2010-02-14 04:09:48
Excellent. Thanks a ton.
Anonymous
2010-03-12 19:44:40
When do you invoke this function?
Anonymous
2010-03-17 05:46:54
the code is good. For someone that doesn't know much about how to implement this into a form; they'll have trouble though.

- James
<a href="http://www.fendza.com">Employee Scheduling Software by Fendza.com</a>
Anonymous
2010-03-17 05:50:26
Forgot to add; may want to add in there a quick how-to on how to not only implement, but also convert it to fit different forms by where to input the id tags.

James
Employee scheduling software by Fendza
Anonymous
2011-02-02 20:38:47
Daily Deals
Anonymous
2011-06-07 16:53:03
nu stiu de astea!!
ObatAsamUrat
2011-06-16 07:15:02
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obat asam urat
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