function.implode NEED HELP :(

Hello,

I am not sure if this is the right section but i can not seem to sort this:

Warning: implode() [function.implode]: Invalid arguments passed in /home/minhyyyr/public_html/welfareuk.co.uk/wp-content/themes/danko/_blog.php on line 47

As far as i can gather the problem lies around here:

<div class=”content-wrap-left left”>
<?php

wp_reset_query();
$blog_category = get_option(THEME_NAME.’_blog_post_category’);
$categories = get_categories(‘orderby=name’);
$include_category = null;
$slug = get_page_link();
ASSUMING THIS IS LINE 47: $allcat = implode(‘,’, $blog_category);

$paged = (get_query_var(‘paged’)) ? get_query_var(‘paged’) : 0;
$args=array(‘cat’=>$allcat, ‘post_status’ => ‘publish’,’paged’ => $paged,’posts_per_page’ => get_option(‘posts_per_page’),’ignore_sticky_posts’=> 1);

Any help would be much appreciated.

Kind Regards

Garry