How to use extract() to get the values of a form?

Question

I'm just learning PHP and I'm following a tutorial. Now I'm on the part where we examine server-side form validation and the tutorial uses the request_import_variables to get the values and validate them. But this method is deprecated now. How can I get the values from a form that are stored in an array? I tried using extract but I'm not that familiar with the syntax and I don't get the result that I want. Here is the code.

<?php
//In this example I'm going to get the values of the form 
//and validate them on the server.
if(isset($_POST['Form'])) {
    //import_request_variables isn't supported anymore by php
    //import_request_variables("p", "z");
    extract($_POST['Form'], EXTR_PREFIX_ALL, "z");
    $missingFields = array();
    $required = array("FName"=>"First Name", "LName"=>"Last Name");

    while(list($var, $val) = each($required)){
        if(isset($zForm[$var]) && $zForm[$var] != ''){
            if(is_string($zForm[$var]))
                print "Everything ok <br />";
            else
                print "You have to provide a valid first and last name <br />";
        }
        else {
            $missingFields[$var] = $val;
        }
    }

    if(count($missingFields)){
        print "You missed out one or more fields:<br />";

        while(list($var, $val) = each($missingFields)){
            print $val . "<br />";
        }
    }
    else {
        print "Form passed!<br />";
        var_dump($zForm['Languages']);
        exit;
    }
}
?>

<form method="post" action="formValidation.php">
First Name: <input type="text" name="Form[FName]" /> (required)<br />
Last Name: <input type="text" name="Form[LName]" /> (required) <br />
Age: <input type="text" name="Form[Age]" /><br /><br />
Languages known:<br />
<input type="checkbox" name="Form[Languages][]" value="PHP" checked="checked"> PHP</input>
<input type="checkbox" name="Form[Languages][]" value="CPP"> C++</input>
<input type="checkbox" name="Form[Languages][]" value="Delphi"> Delphi</input>
<input type="checkbox" name="Form[Languages][]" value="Java"> Java</input>
<input type="submit" />

As a result I get You missed one or more fields First Name Last Name

Here is the section of the tutorial I'm stuck

There's no need to extract it in the first place. You can just localize the input array per `$form = $_REQUEST["Form"];` to access fields more conveniently. (Nothing wrong with `extract()` per se. But you really should avoid it in the global scope - which is what this excerpt looks like.) — mario, Sep 01 '15 at 14:02
It kind of worked with the tip that you gave me. But when I put a number as a name the form still passes. Do the values get converted to strings and put in the array? For example I can put 1234 as a name and I will get the result "Form passed" — captain, Sep 01 '15 at 14:25
You are making an assignment in each of your while loops (`list($var, $val) = each($required)`) which should be `list($var, $val) == each($required)`. — Ahmad Baktash Hayeri, Sep 01 '15 at 14:31
No it should be `=` because that is how you traverse a list with each. If you put `==` you get an error. — captain, Sep 01 '15 at 14:34
@captain Yes. All request vars will come across as strings or arrays of strings/arrays (if they are nested or you have multiple input elements with the same `name` attribute). For numbers you can use `is_numeric` or `ctype_digit` to check that the value is numeric, then if you need to be really strict you can cast it to the numeric type you are expecting and validate it against more specific rules. Or you could just convert it and then check that. Depends on what you are trying to validate. — prodigitalson, Sep 01 '15 at 21:33

score 2 · Answer 1 · edited May 23 '17 at 10:26

Avoid extracting variables! Instead of this you should work with array directly. Discussion about this bad extract practice is here.

As for your, code, you made a little mistake here:

extract($_POST['Form'], EXTR_PREFIX_ALL, "z");

This extract will make variables from $_POST['Form'] array, such as $z_FName, $z_LName, $z_Age, etc.

The code from tutorial:

import_request_variables("p", "z");

This import_request_variables will make variables from $_POST array, so it will be just $z_Form.

So you need change

extract($_POST['Form'], EXTR_PREFIX_ALL, "z");

to

extract($_POST, EXTR_PREFIX_ALL, "z");

And change $zForm to $z_Form.

If you'll debug such cases, you may have a look to a get_defined_vars function.

I would move the warning about extract to the beginning of your answer, and bold it. Then follow up. — prodigitalson, Sep 01 '15 at 21:40

How to use extract() to get the values of a form?

1 Answers1