Replaces smart quotes with quotation marks when adding shortcodes to WordPress content

scrub-smart-quotes.php

/**
 * Scrubs content for curly quotes
 * @param  string $content 
 * @return string         
 */
function prefix_scrub_smart_quotes_from_shortcodes( $content ){

  // Search for all smartquotes inside of shortcodes and replace them
  $content = preg_replace('/(“|”)(?=[^\[]*\])/', '"', $content );

  return $content;
}
add_filter( 'content_save_pre', 'prefix_scrub_smart_quotes_from_shortcodes' );