How to use author meta in shortcode?

Question

I am trying to create a shortcode that will return a link to a book on Amazon with a specific affiliate tracking code specific to the author. I created a user option called "amz" to hold the author's tracking code. This works fine when I'm using it elsewhere. This is the shortcode I created:

function amazon_link_function($atts, $content = null) { extract(shortcode_atts(array( 'isbn' => ' ', 'title' => ' ' ), $atts));

  $amztrack = the_author_meta( 'amz' );

  return '<a href="http://www.amazon.com/exec/obidos/ASIN/' .$isbn. '/' .$amztrack. '" title="' .$title. '" target="_blank">' .$title. '</a>';

} add_shortcode("amazon", "amazon_link_function");

The isbn and title values return properly, but the tracking code stored in the $amztrack variable is displayed as plain text before the paragraph the shortcode is used in:(

I also tired this for the return line and got the same result:

  return '<a href="http://www.amazon.com/exec/obidos/ASIN/' .$isbn. '/' .the_author_meta( 'amz' ). '" title="' .$title. '" target="_blank">' .$title. '</a>';

Answer 1

the_author_meta() prints the content immediately. Use instead:

$amztrack = get_the_author_meta( 'amz', FALSE );

This will return the value.

Answer 2

shortcodes need to return the value, therefore you cannot use a function which prints the output, like the_author_meta();

use get_the_author_meta() http://codex.wordpress.org/Function_Reference/get_the_author_meta