why do I lose access to php variables when I render a new page

Question

I have a render function that looks like:

function render($template, $values = array()){

   // if template exists, render it
   if (file_exists("../views/$template")){

      // extract variables into local scope
      extract($values);

      // render header_form
      require("../views/header_form.php");

      // render template
      require("../views/$template");

      // render footer
      require("../views/footer_form.php");

   }else{

      // else err
      trigger_error("Invalid template: $template", E_USER_ERROR);

   }
}

Suppose I have a script crew.php that looks like this:

<?php

    require('../includes/config.php');
        $values=[];           

        $today = new DateTime();

        render('crew_form.php',$values);

?>

Why don't I have access to $today in crew_form.php? For instance, if crew_form.php was:

<?php

    echo $today;
?>

When you use require doesn't that just add the script to the existing code? Is it because of local scope of the function render()?

you need to set it into `$values['today'] = $today` (then you need to use `->format(...)` you cant simply echo an object).. basically your passing `$values` to a function, and extract.. extracts what's in `$values`, so the keys are the variables — Lawrence Cherone, Oct 10 '21 at 21:37
reread the question, you are not understanding what is being asked — DCR, Oct 10 '21 at 21:40

LSerni · Accepted Answer · 2021-10-10T21:54:48.287

1

You don't have access to $today because you're out of scope. The variable is defined outside a function, and is not available inside it -- and render() is a function.

You can obviate the problem with the use keyword, or by abusing the global directive, but a better way to avoid polluting the scope would be passing the variables explicitly and reading them with extract().

Which is exactly what your code was attempting doing, using $values. But you need to put $today inside $values and pass it to render():

$values['today'] = $today;

Now, a variable called $today will be available in crew-form.php, but it will not be the same $today even if it will start as a copy of the same value. You can see it better like this:

$values['today2'] = $today;

Inside crew-form.php, $today2 will exist, $today will not, because the latter is "out of scope".

Changes to the extracted values will be lost upon exit from render (you can use EXTR_REFS but that adds complications).

edited Oct 10 '21 at 21:54

answered Oct 10 '21 at 21:46

LSerni

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you mean inside crew_form.php don't you? – DCR Oct 10 '21 at 21:48
`crew_form.php` remains inchanged – Cid Oct 10 '21 at 21:48
wasn't my upvote as your answer was bonkers – DCR Oct 10 '21 at 21:51
@DCR okay, tried to salvage the answer as I can't delete an accepted answer. – LSerni Oct 10 '21 at 21:55
no problem, appreciate your help. – DCR Oct 10 '21 at 22:21

score 0 · Answer 2 · answered Oct 10 '21 at 21:42

PHP is sometimes called 'shared nothing'. In a single HTTP request, everything gets built up from scratch, and after the request is complete all memory is released.

If you want information to carry over between requests, you need a storage mechanism such as a database. This is by design and always has been the case for PHP.

score 0 · Answer 3 · answered Oct 10 '21 at 21:46

0

It would appear that my hunch is correct. If $today was created in the render function we can indeed print it out in crew_form.php.

answered Oct 10 '21 at 21:46

DCR

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why do I lose access to php variables when I render a new page

3 Answers3