Drupal multiple variables in block content

I am trying to print out multiple variables in a block content, but drupal returns:

Parse error: syntax error, unexpected '$search_field' (T_VARIABLE) in C:\seu\xampp\htdocs\iptp\sites\all\modules\custom\lasearch\lasearch.module on line 70

Here is my Code:

/**
 * Implements hook_block_view
 * 
 * This creates a block which shows the search results
 * 
 * @param type $delta
 * @return type
 */
function lala_search_block_view($delta = '') {
    $block = array();

    switch ($delta) {
        case 'lala_SEARCH_RESULT':

            $block['content'] = array(
                '#markup' => _lala_search_search_page(),
            );
            return $block;
            break;
    }
    switch ($delta) {
        case 'lala_lanavigator':
        $search_field = module_invoke('search', 'block_view', 'search');
        $search_text = _lala_search_get_laavigator('prefix');
            $block['title'] = t('la-Navigator');
            $block['content'] = $search_text $search_field['content'];
            return $block;
            break;
    }
}

I am new to PHP and I am britty sure that the problem depends on my syntax :-/