Pre-populating of form fields not working like it should

[MockY]

I am using file_get_contents() and preg_match() in order to extract specific information from a public database. This information is stored in variables for being used in populating a form automatically. The process is as follows: The user is presented with an empty form. Instead of having to fill out all the fields by hand, the user has an option of entering a number in one of the fields and by clicking a button, the form will fetch information based on that number from the public database and populate some of the fields with this information.

 

I have in mostly figured out, but there is one thing I don't really understand why it wont work. If I store the entire form in a variable and later print it out once the form is processed, the variables can't be used as values for the fields. But if I echo out the form as a string, then I can. That part simply don't make sense. Let me demonstrate.

 

The following will not display the fetched address in the field once the form is run

$form = ' <form method="post" action="testing.php">
            <table >
                <tr>
                    <td>License #</td>
                    <td>Street 1</td>
                </tr>
                <tr>
                    <td><input type="text" name="licenumber" value="" style="width:150px;" /></td>
                    <td><input type="text" name="street1" value="'. $extractedaddress .'" style="width:150px;" /></td>
                 </tr>

            </table>
         <input type="submit" name="test" value="Process" />
        </form>';

if (isset ($_POST['test'])) {

// Grab the address based on the number from the website using file_get_contents
// Store the address in a variable
$extractedaddress = '1234 Some Street';
}

echo $form;

} else {
    echo $form;
}

 

The following does work just fine and is practically the same thing. But instead of echoing out the $form variable, I echo out the form itself. In my book, this is the same as above, but for some reason it works

 

$form = '
        <form method="post" action="testing.php">
            <table >
                <tr>
                    <td>License #</td>
                    <td>Street 1</td>
                </tr>
                <tr>
                    <td><input type="text" name="licenumber" value="" style="width:150px;" /></td>
                    <td><input type="text" name="street1" value="'. $extractedaddress .'" style="width:150px;" /></td>
                 </tr>

            </table>
         <input type="submit" name="test" value="Process" />
        </form>
      ';


if (isset ($_POST['test'])) {

// Grab the address based on the number from the website using file_get_contents
// Store the address in a variable
$extractedaddress = '1234 Some Street';

}

echo '<form method="post" action="testing.php">
            <table >
                <tr>
                    <td>License #</td>
                    <td>Street 1</td>
                </tr>
                <tr>
                    <td><input type="text" name="licenumber" value="" style="width:150px;" /></td>
                    <td><input type="text" name="street1" value="'. $extractedaddress .'" style="width:150px;" /></td>
                 </tr>

            </table>
         <input type="submit" name="test" value="Process" />
        </form>';

} else {
    echo $form;
}

 

Why does the second work but not the first example, and what can I do to make it work?

[wildteen88]

You must define variables before you can use them. PHP does not backtrack. To fix the issue place your form proccessing code before you define the form, eg

 

if (isset ($_POST['test'])) 
{
// Grab the address based on the number from the website using file_get_contents
// Store the address in a variable
$extractedaddress = '1234 Some Street';
}

$form = ' <form method="post" action="testing.php">
            <table >
                <tr>
                    <td>License #</td>
                    <td>Street 1</td>
                </tr>
                <tr>
                    <td><input type="text" name="licenumber" value="" style="width:150px;" /></td>
                    <td><input type="text" name="street1" value="'. $extractedaddress .'" style="width:150px;" /></td>
                 </tr>

            </table>
         <input type="submit" name="test" value="Process" />
        </form>';

echo $form;

 

[MockY]

But since $form contains a variable call and is printed out at the same place as the form itself, in my mind, that would be the same thing. Either way, thanks for you help. I will put the processing code on top of my pages from now on.

[wildteen88]

PHP will call for the variable $extractedaddress while your defining your $form variable. Not when you're going to use the $form variable. This is why it is important to make sure you're defining variables before you use them.