page content function for wp_insert_post - wordpress

Question

I want to add two text fields of username and password in the page content. Basically i am making my plugin. I have made a page which is connected to my plugin. I want to add content in this page by using function.
my page code is:
register_activation_hook( __FILE__, 'my_plugin_install_function');
function my_plugin_install_function() {
$post = array(
'page_template' => '',
'comment_status' => 'closed',
'ping_status' => 'closed' ,
'post_author' => 1,
'post_date' => date('Y-m-d H:i:s'),
'post_name' => 'Checklists',
'post_status' => 'publish' ,
'post_title' => 'Checklists',
'post_type' => 'page',
'post_content' => 'my_function()'
);//insert page and save the id
$newvalue = wp_insert_post( $post, false ); //save the id in the database
update_option( 'hclpage', $newvalue );
}
my_function()
{
// A login form will be here.
}
Is it possible ??? what will be the best way to do it in the plugin file of wordpress ???

Answer 1

To add content I did not use function. But I use php variable.
$form = '<form action="..../wp-content/plugins/wp-link-with-parse/php-sdk/test.php" method="post">
<label for="username">Username:</label>
<input type="text" id="username" name="username">
<label for="password">Password:</label>
<input type="password" id="password" name="password">
<div id="lower">
<input type="submit" name="login" value="Login">
</form>';
to assign content use:
'post_content'=> $form

Answer 2

i know this post is from 5 years ago, but i'm currently trying to do a wordpress plugin, and i found a solution for adding content to a custom page in wordpress, what i did is to create a .php file with all the content, including php code, and then include that code in my post_type page by creating a variable and adding that file to that variable with file_get_contents, something like this:
enter image description here
hope it can be useful