Working of foreach loop with array

Question

I'm trying to understand a piece of code I found online to create customized user login page. Here I'm unable to understand how foreach loop works (specially this line: $page_definitions as $slug => $page in foreach argument). I'm very new to working with arrays and am trying to learn how it works.

class Personalize_Login_Plugin {

    public static function plugin_activated() {
        // Information needed for creating the plugin's pages
        $page_definitions = array(
            'member-login' => array(
                'title' => __( 'Sign In', 'personalize-login' ),
                'content' => '[custom-login-form]'
            ),
            'member-account' => array(
                'title' => __( 'Your Account', 'personalize-login' ),
                'content' => '[account-info]'
            ),
        );

        foreach ( $page_definitions as $slug => $page ) {
            // Check that the page doesn't exist already
            $query = new WP_Query( 'pagename=' . $slug );
            if ( ! $query->have_posts() ) {
                // Add the page using the data from the array above
                wp_insert_post(
                    array(
                        'post_content'   => $page['content'],
                        'post_name'      => $slug,
                        'post_title'     => $page['title'],
                        'post_status'    => 'publish',
                        'post_type'      => 'page',
                        'ping_status'    => 'closed',
                        'comment_status' => 'closed',
                    )
                );
            }
        }
    }
    public function __construct() {

    }
}

Answer 1

When I first started working with foreach loops, this particular syntax seemed mysterious to me, too, and it wasn't until I needed it that its usefulness became obvious. Works that way for a lot of "things you see in code."

Anyway, to answer the question, in the sample code, using as $key => $value makes the key ($slug) available as a variable in the ensuing code block. The $page_definitions array has two top-level keys, 'member-login' and 'member-account' which (after an already-exists? check) become the slugs for two new pages that the function creates (inserts) with the values of the two-member ('title' and 'content') arrays or sub-arrays as the new pages' title and content: one entitled "Sign In" with content the shortcode [custom-login-form], and one entitled "Your Account" with [account-info] shortcode.

So, if I were on that site, after the function ran, I'd find two pages, one with a slug of siteurl/member-login, entitled Sign In, showing a custom login form, etc., and a second page with a slug siteurl/member-account, with content created by the account-info shortcode. The two shortcodes probably produce differentiated content based on logged-in status and identity of the user.

Got it? [EDITED AND FIXED after I screwed up the answer the first time!]