Bootstrap Buttons via Wordpress shortcode

functions.php

add_shortcode( 'button', 'wpbs_button', 10, 2 );
if ( ! function_exists( 'wpbs_button' ) ) {
  /**
   * Custom Button
   *
   * Add an inline button to content, with customizeable CSS classes, and
   * link to a page by `page-id` or URL.
   *
   * [button class="btn-primary"]My Button Text[/button]
   *
   * @param array $atts Button attributes
   * @param string $content Button text content
   *
   * @return string Button HTML
   */
  function wpbs_button( $atts, $content ) {
    if ( function_exists( 'openssl_random_pseudo_bytes' ) && function_exists( 'bin2hex' ) ) {
      $rand = bin2hex( openssl_random_pseudo_bytes( 8 ) );;
    } else {
      $rand = rand( 1000, 9999 );
    }

    $a = shortcode_atts( array(
      'attr'      => false,               // Additional attributes as Key:Value pairs, comma separated
      'class'     => 'btn-primary',       // CSS classes for button element
      'hash'      => false,               // #string
      'icon'      => false,               // not used
      'icon-url'  => false,               // not used
      'id'        => 'button-' . $rand,   // button id
      'logged-in' => false,               // is user logged in?
      'modal'     => false,               // Bootstrap modal target
      'page-id'   => false,               // Page ID of linked page
      'query'     => false,               // URL query params
      'target'    => '',                  // Attr: target="_blank"
      'url'       => '#'                  // Linked page URL
    ), $atts );

    $attributes_array = array();
    if ( $a['attr'] ) {
      $attribs = explode( ",", $a['attr'] );
      foreach ($attribs as $attrib) {
        if ( strpos( $attrib, ':' ) !== false ) {
          $arr = explode( ":", $attrib );
          $attributes_array[ $arr[0] ] = $arr[1];
        }
      }
    }
    $attributes_string = null;
    foreach ($attributes_array as $key => $value) {
      $attributes_string .= sprintf( '%1$s="%2$s" ', $key, $value );
    }

    $target = null;
    if ( in_array( $a['target'], array( 'blank', '_blank' ) ) )
      $target = 'target="_blank"';

    if ( $a['modal'] )
      $target = 'data-toggle="modal" data-target="' . $a['modal'] . '"';

    // if page-id attribute is set, use that instead of link, otherwise, use link attribute.
    $url = ( $a['page-id'] && 'publish' === get_post_status( $a['page-id'] ) ? get_permalink( $a['page-id'] ) : esc_html( $a['url'] ) );

    $hash = null;
    if ( $a['hash'] ) {
      $hash .= '#' . rawurlencode( $a['hash'] );
    }

    $query = null;
    if ( $a['query'] ) {
      $query .= '?' . rawurlencode( $a['query'] );
    }

    // Build the button HTML
    
    $button_html = sprintf( '<a href="%1$s" id="%2$s" class="btn %3$s" %4$s>%5$s</a>',
      $url . $hash . $query,                                // build the URL
      esc_html( $a['id'] ),
      esc_html( $a['class'] ),
      $attributes_string . ' ' . $target,                   // build attributes
      sprintf( '<span>%1$s</span>', esc_html( $content ) )
    );

    return $button_html;
  }
}