Sends a confirmation request email when a change of site admin email address is attempted.

The new site admin address will not become active until confirmed.

function update_option_new_admin_email( $old_value, $value ) {
	if ( get_option( 'admin_email' ) === $value || ! is_email( $value ) ) {
		return;
	}

	$hash            = md5( $value . time() . wp_rand() );
	$new_admin_email = array(
		'hash'     => $hash,
		'newemail' => $value,
	);
	update_option( 'adminhash', $new_admin_email );

	$switched_locale = switch_to_locale( get_user_locale() );

	/* translators: Do not translate USERNAME, ADMIN_URL, EMAIL, SITENAME, SITEURL: those are placeholders. */
	$email_text = __(
		'Howdy ###USERNAME###,

Someone with administrator capabilities recently requested to have the
administration email address changed on this site:
###SITEURL###

To confirm this change, please click on the following link:
###ADMIN_URL###

You can safely ignore and delete this email if you do not want to
take this action.

This email has been sent to ###EMAIL###

Regards,
All at ###SITENAME###
###SITEURL###'
	);

	/**
	 * Filters the text of the email sent when a change of site admin email address is attempted.
	 *
	 * The following strings have a special meaning and will get replaced dynamically:
	 * ###USERNAME###  The current user's username.
	 * ###ADMIN_URL### The link to click on to confirm the email change.
	 * ###EMAIL###     The proposed new site admin email address.
	 * ###SITENAME###  The name of the site.
	 * ###SITEURL###   The URL to the site.
	 *
	 * @since MU (3.0.0)
	 * @since 4.9.0 This filter is no longer Multisite specific.
	 *
	 * @param string $email_text      Text in the email.
	 * @param array  $new_admin_email {
	 *     Data relating to the new site admin email address.
	 *
	 *     @type string $hash     The secure hash used in the confirmation link URL.
	 *     @type string $newemail The proposed new site admin email address.
	 * }
	 */
	$content = apply_filters( 'new_admin_email_content', $email_text, $new_admin_email );

	$current_user = wp_get_current_user();
	$content      = str_replace( '###USERNAME###', $current_user->user_login, $content );
	$content      = str_replace( '###ADMIN_URL###', esc_url( self_admin_url( 'options.php?adminhash=' . $hash ) ), $content );
	$content      = str_replace( '###EMAIL###', $value, $content );
	$content      = str_replace( '###SITENAME###', wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ), $content );
	$content      = str_replace( '###SITEURL###', home_url(), $content );

	if ( '' !== get_option( 'blogname' ) ) {
		$site_title = wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES );
	} else {
		$site_title = parse_url( home_url(), PHP_URL_HOST );
	}

	wp_mail(
		$value,
		sprintf(
			/* translators: New admin email address notification email subject. %s: Site title. */
			__( '[%s] New Admin Email Address' ),
			$site_title
		),
		$content
	);

	if ( $switched_locale ) {
		restore_previous_locale();
	}
}