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); ?>

      You can now retrieve these options, along with another one that does not exist, and see what variable types are returned, shown as an inline comment below each get_option() call:

      <?php var_dump( get_option( 'nonexistent_option' ) ); // bool(false) var_dump( get_option( 'pdev_bool_true' ) ); // string(1) "1" var_dump( get_option( 'pdev_bool_false' ) ); // bool(false) ?>

To avoid an error when checking option values, you should store true and false as 1 and 0. This means also that you need to strictly compare the return of get_option() with Boolean false to check if the option exists.

      <?php //set the option as true update_option( 'pdev_plugin_enabled', 1 ); if( get_option( 'pdev_plugin_enabled' ) == false ) { // option has not been defined yet // ... echo 'NOT DEFINED YET'; } else { // option exists // ... echo 'OPTION EXISTS!'; } ?>

      You can also specify what value you want to be returned if the option is not found in the database, with a second option parameter to get_option(), like in the following example:

      <?php $option = get_option( 'pdev_plugin_option', 'Option not found' ); ?>

      Loading an Array of Options

      You have seen that saving multiple options in a single array is best practice. A complete example of saving and then getting values from one array would be as follows:

      <?php // To store all of them in a single function call: $options = array( 'color' => 'red', 'fontsize' => '120%', 'border' => '2px solid red' ); update_option( 'pdev_plugin_options', $options ); // Now to fetch individual values from one single call: $options = get_option( 'pdev_plugin_options' ); // Store individual option values in variables $color = $options[ 'color' ]; $fontsize = $options[ 'fontsize' ]; $border = $options[ 'border' ]; ?>

      Saving and retrieving options enclosed in an array has another advantage: variable Boolean types within the array are preserved. Consider the following example:

<?php add_option( 'pdev_test_bool', array( 'booltrue' => true, 'boolfalse' => false ) ); ?>

      Now get the option value from the database with var_dump( get_option( 'test_bool' ) ). See how Boolean types are retained, contrary to the previous example:

      // output result var_dump( get_option( 'pdev_test_bool' ) ); array(2) { ["booltrue"] => bool(true) ["boolfalse"]=> bool(false) }

      Deleting Options

      Now that you understand how to create, update, and retrieve options, let's look at deleting an option. Deleting an option needs a self‐explanatory function call.

      <?php delete_option( 'pdev_plugin_options' ); ?>

      This function call returns false if the option to delete cannot be found and returns true otherwise. You will mostly delete options when writing uninstall functions or files (see Chapter 2).

      The Autoload Parameter

      By default, all the options stored in the database are fetched by a single SQL query when WordPress initializes and then caches. This applies to internal WordPress core settings and options created and stored by plugins.

      This is efficient behavior: no matter how many get_option() calls you issue in your plugins, they won't generate extra SQL queries and slow down the whole site. Still, the potential drawback of this autoload technique is that rarely used options are always loaded in memory, even when not needed. For instance, there is no point in fetching backend options when a reader accesses a blog post.

      To address this issue when saving an option for the first time, you can specify its autoload behavior, as in the following example:

      <?php add_option( 'pdev_plugin_option', $value, '', $autoload ); ?>

      Note the empty third parameter: This is a parameter that was deprecated several WordPress versions ago and is not needed any more. Any value passed to it will do; just be sure not to omit it.

The fourth parameter is what matters here. If $autoload is anything but 'no' (or simply not specified), option pdev_plugin_option will be read when WordPress starts, and subsequent get_option() function calls will not issue any supplemental SQL query. Setting $autoload to 'no' can invert this: this option will not be fetched during startup of WordPress, saving memory and execution time, but it will trigger an extra SQL query the first time your code fetches its value.

      NOTE If you want to specify the autoload parameter, you need to use add_option() instead of update_option() when creating an option the first time. If you don't need this parameter, always using update_option() to both create and update will make your code more simple and consistent.

      Of course, specifying the autoload parameter upon creation of an option does not change the way you fetch, update, or delete its value.

      Segregating Plugin Options

      A function to initiate your plugin options, run on plugin activation as covered in Chapter 2, could then look like the following:

      <?php function pdev_plugin_create_options() { // front-end options: autoloaded add_option( 'pdev_plugin_options', array( 'color' => 'red', 'fontsize' => '120%', 'border' => '2px solid red' ) ); // back-end options: loaded only if explicitly needed add_option( 'pdev_plugin_admin_options', array( 'version' => '1.0', 'donate_url' => 'https://example.com/', 'advanced_options' => '1' ), '', 'no' ); } ?>

      Again, don't forget the empty third parameter before the autoload value. This might seem a bit convoluted, and actually it is for so few options set. This professional technique makes sense if your plugin features dozens of options, or options containing long text strings.

      NOTE As a rule of thumb, if your options are needed by the public part of the blog, save them with autoload. If they are needed only in the admin area, save them without autoload.

      Toggling the Autoload Parameter

      The autoload parameter is set when an option is created with add_option() and is not supposed to change afterward. With this said, if you believe that it would improve your plugin's efficiency to modify the autoload behavior, it is possible and easy: simply delete and then re‐create the option with an explicit autoload parameter.

      <?php function pdev_plugin_recreate_options() { // get old value $old = get_option( 'pdev_plugin_admin_options' ); // delete then recreate without autoload delete_option( 'pdev_plugin_admin_options' ); add_option( 'pdev_plugin_admin_options', $old, '', 'no' ); } ?>

THE SETTINGS API

      Options can be internally created and updated by your plugin (for instance, storing the time stamp of the next iteration of a procedure). But they are also frequently used to store settings the end user will modify through your plugin administration page.

      When creating or updating user‐defined options for a plugin, relying on the Settings API can make your code both simpler and more efficient.

      Benefits of the Settings API

      Dealing with user inputs introduces new constraints in the option process: you need to design

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