Custom Placeholder

Each placeholder is defined with a class responsible for replacing a specific string tag with a dynamic value. Placeholder class needs to extend EasyWatermark\Placeholders\Abstracts\Placeholder and should implement the following methods:

1. resolve - returning the value of the placeholder

2. validate - checking if the value is correct

3. sanitize - sanitizing the value

There are also 4 abstract placeholders available that implement the validate and sanitize methods for a given value type:

1. EasyWatermark\Placeholders\Abstracts\EmailPlaceholder

2. EasyWatermark\Placeholders\Abstracts\IntegerPlaceholder

3. EasyWatermark\Placeholders\Abstracts\StringPlaceholder

4. EasyWatermark\Placeholders\Abstracts\UrlPlaceholder

Placeholder class

use EasyWatermark\Placeholders\Abstracts\StringPlaceholder;

/**
 * Abstract placeholder
 */
class FavoriteColorPlaceholder extends StringPlaceholder {

	/**
	 * Constructor
	 *
	 * @return void
	 */
	public function __construct() {

		$this->slug    = 'favorite_color';
		$this->name    = __( 'Favorite color', 'textdomain' );
		$this->example = __( 'blue', 'textdomain' );

	}

	/**
	 * Resolves placeholder
	 *
	 * @param  EasyWatermark\Placeholders\Resolver $resolver Placeholders resolver instance.
	 * @return string
	 */
	public function resolve( $resolver ) {

		$user = wp_get_current_user();
		return get_user_meta( 'favorite_color', $user->ID );

	}
}

The above class will replace a %favorite_color% string in the watermark text with the value of a favorite_color meta for logged-in user.

Registering the Placeholder

/**
 * @param EasyWatermark\Placeholders\Resolver $resolver Placeholders resolver instance.
 */
add_action( 'easy-watermark/placeholders/load', function ( $resolver ) {
    // Add custom placeholder instance to the resolver.
    $resolver->add_placeholder( new FavoriteColorPlaceholder() );
} );