list_core_update() WordPress Function

function list_core_update( $update ) {
	global $wp_local_package, $wpdb;
	static $first_pass = true;

	$wp_version     = get_bloginfo( 'version' );
	$version_string = sprintf( '%s–%s', $update->current, get_locale() );

	if ( 'en_US' === $update->locale && 'en_US' === get_locale() ) {
		$version_string = $update->current;
	} elseif ( 'en_US' === $update->locale && $update->packages->partial && $wp_version == $update->partial_version ) {
		$updates = get_core_updates();
		if ( $updates && 1 === count( $updates ) ) {
			// If the only available update is a partial builds, it doesn't need a language-specific version string.
			$version_string = $update->current;
		}
	} elseif ( 'en_US' === $update->locale && 'en_US' !== get_locale() ) {
		$version_string = sprintf( '%s–%s', $update->current, $update->locale );
	}

	$current = false;
	if ( ! isset( $update->response ) || 'latest' === $update->response ) {
		$current = true;
	}

	$message       = '';
	$form_action   = 'update-core.php?action=do-core-upgrade';
	$php_version   = phpversion();
	$mysql_version = $wpdb->db_version();
	$show_buttons  = true;

	// Nightly build versions have two hyphens and a commit number.
	if ( preg_match( '/-\w+-\d+/', $update->current ) ) {
		// Retrieve the major version number.
		preg_match( '/^\d+.\d+/', $update->current, $update_major );
		/* translators: %s: WordPress version. */
		$submit = sprintf( __( 'Update to latest %s nightly' ), $update_major[0] );
	} else {
		/* translators: %s: WordPress version. */
		$submit = sprintf( __( 'Update to version %s' ), $version_string );
	}

	if ( 'development' === $update->response ) {
		$message = __( 'You can update to the latest nightly build manually:' );
	} else {
		if ( $current ) {
			/* translators: %s: WordPress version. */
			$submit      = sprintf( __( 'Re-install version %s' ), $version_string );
			$form_action = 'update-core.php?action=do-core-reinstall';
		} else {
			$php_compat = version_compare( $php_version, $update->php_version, '>=' );
			if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $wpdb->is_mysql ) ) {
				$mysql_compat = true;
			} else {
				$mysql_compat = version_compare( $mysql_version, $update->mysql_version, '>=' );
			}

			$version_url = sprintf(
				/* translators: %s: WordPress version. */
				esc_url( __( 'https://wordpress.org/support/wordpress-version/version-%s/' ) ),
				sanitize_title( $update->current )
			);

			$php_update_message = '</p><p>' . sprintf(
				/* translators: %s: URL to Update PHP page. */
				__( '<a href="%s">Learn more about updating PHP</a>.' ),
				esc_url( wp_get_update_php_url() )
			);

			$annotation = wp_get_update_php_annotation();

			if ( $annotation ) {
				$php_update_message .= '</p><p><em>' . $annotation . '</em>';
			}

			if ( ! $mysql_compat && ! $php_compat ) {
				$message = sprintf(
					/* translators: 1: URL to WordPress release notes, 2: WordPress version number, 3: Minimum required PHP version number, 4: Minimum required MySQL version number, 5: Current PHP version number, 6: Current MySQL version number. */
					__( 'You cannot update because <a href="%1$s">WordPress %2$s</a> requires PHP version %3$s or higher and MySQL version %4$s or higher. You are running PHP version %5$s and MySQL version %6$s.' ),
					$version_url,
					$update->current,
					$update->php_version,
					$update->mysql_version,
					$php_version,
					$mysql_version
				) . $php_update_message;
			} elseif ( ! $php_compat ) {
				$message = sprintf(
					/* translators: 1: URL to WordPress release notes, 2: WordPress version number, 3: Minimum required PHP version number, 4: Current PHP version number. */
					__( 'You cannot update because <a href="%1$s">WordPress %2$s</a> requires PHP version %3$s or higher. You are running version %4$s.' ),
					$version_url,
					$update->current,
					$update->php_version,
					$php_version
				) . $php_update_message;
			} elseif ( ! $mysql_compat ) {
				$message = sprintf(
					/* translators: 1: URL to WordPress release notes, 2: WordPress version number, 3: Minimum required MySQL version number, 4: Current MySQL version number. */
					__( 'You cannot update because <a href="%1$s">WordPress %2$s</a> requires MySQL version %3$s or higher. You are running version %4$s.' ),
					$version_url,
					$update->current,
					$update->mysql_version,
					$mysql_version
				);
			} else {
				$message = sprintf(
					/* translators: 1: Installed WordPress version number, 2: URL to WordPress release notes, 3: New WordPress version number, including locale if necessary. */
					__( 'You can update from WordPress %1$s to <a href="%2$s">WordPress %3$s</a> manually:' ),
					$wp_version,
					$version_url,
					$version_string
				);
			}

			if ( ! $mysql_compat || ! $php_compat ) {
				$show_buttons = false;
			}
		}
	}

	echo '<p>';
	echo $message;
	echo '</p>';

	echo '<form method="post" action="' . esc_url( $form_action ) . '" name="upgrade" class="upgrade">';
	wp_nonce_field( 'upgrade-core' );

	echo '<p>';
	echo '<input name="version" value="' . esc_attr( $update->current ) . '" type="hidden" />';
	echo '<input name="locale" value="' . esc_attr( $update->locale ) . '" type="hidden" />';
	if ( $show_buttons ) {
		if ( $first_pass ) {
			submit_button( $submit, $current ? '' : 'primary regular', 'upgrade', false );
			$first_pass = false;
		} else {
			submit_button( $submit, '', 'upgrade', false );
		}
	}
	if ( 'en_US' !== $update->locale ) {
		if ( ! isset( $update->dismissed ) || ! $update->dismissed ) {
			submit_button( __( 'Hide this update' ), '', 'dismiss', false );
		} else {
			submit_button( __( 'Bring back this update' ), '', 'undismiss', false );
		}
	}
	echo '</p>';

	if ( 'en_US' !== $update->locale && ( ! isset( $wp_local_package ) || $wp_local_package != $update->locale ) ) {
		echo '<p class="hint">' . __( 'This localized version contains both the translation and various other localization fixes.' ) . '</p>';
	} elseif ( 'en_US' === $update->locale && 'en_US' !== get_locale() && ( ! $update->packages->partial && $wp_version == $update->partial_version ) ) {
		// Partial builds don't need language-specific warnings.
		echo '<p class="hint">' . sprintf(
			/* translators: %s: WordPress version. */
			__( 'You are about to install WordPress %s <strong>in English (US).</strong> There is a chance this update will break your translation. You may prefer to wait for the localized version to be released.' ),
			'development' !== $update->response ? $update->current : ''
		) . '</p>';
	}

	echo '</form>';

}