Add some custom CSS to every page to change the style of the entire application.

function redcap_every_page_top($project_id)
{
    ?><link rel="stylesheet" type="text/css" href="/plugins/fancy/style.css" media="screen"><?php
}

Add some custom session variables to be used for only by specific users for every PHP script in REDCap.

function redcap_every_page_top($project_id)
{
    // Set a value based upon the logged-in user's username
    if (SUPER_USER || USERID == 'paul.harris')
    {
        // Use this session variable in other hooks to perform a specic action/behavior
        $_SESSION['show_special_features'] = true;
    }
}

Add some page-specific logic to perform things only for specific pages in REDCap. Note: You can use the PAGE constant to refer to specific PHP scripts within subdirctories in the REDCap version directory (e.g., redcap_vX.X.X) in which they will always have the format SubdirectoryName/my_php_script.php.

function redcap_every_page_top($project_id)
{
    // Do something on the Online Designer page
    if (PAGE == 'Design/online_designer.php')
    {
        // ...
    }

    // Do something on the File Repository page but only for a specific project
    elseif ($project_id == 759 && PAGE == 'FileRepositoryController:index')
    {
        // ...
    }
}

Incorporate calls to a framework or helper scripts that you wish to utilize throughout REDCap on every page.

function redcap_every_page_top($project_id)
{
    // Call the framework class (this is just an example of how this methodology *might* look)
    require "/framework_path/my_framework.php";

    // Instantiate the object to use as a global variable in other hooks or plugins throughout REDCap.
    $framework = new FrameworkObject();
}

This example shows a simple way of performing project-specific actions using the $project_id parameter. NOTE: This particular method is not as clean or as easy to maintain for many projects at once. See the next example for a better way to implement project-specific actions for many projects.

function redcap_every_page_before_render($project_id)
{
    // Perform certain actions for specific projects (using "switch" or "if" statements).
    switch ($project_id) {

        // Perform operations for project_id 212
        case 212:
            // do something specific for this project ...
            break;

        // Perform operations for project_id 4775
        case 4775:
            // do something specific for this project ...
            break;

        // ...
    }
}

A much more manageable way to perform project-specific operations for many projects at once is to create a directory structure where each project has its own subdirectory under the main Hooks directory (e.g., named "redcap/hooks/pid{$project_id}/redcap_survey_page.php"). This allows the code for each project to be sandboxed and separated and also makes it more manageable to utilize other files (e.g., PHP, HTML, CSS, and/or JavaScript files) that you can keep in the project's subdirectory (i.e., "pid{$project_id}") in the Hooks folder. Then the designated project handler PHP script can utilize any of the parameters passed in the function to perform actions specific to each project. NOTE: This example assumes that the "hooks" sub-directory is located in the same directory as the PHP file containing the Hook functions.