Foreach implode issue

Change it to:

<?php
$guiones  = rwmb_meta( 'mb_guionistas', array( 'multiple' => true) );
$pieces = array();

foreach ($guiones as $item) {
    $pieces [] = '<a href="' . get_bloginfo('url') . '/?p=' . $item . '" title="">' . get_the_title( $item ) . '</a>';
}

echo implode(', ', $pieces);
?>

bloginfo() echos values while get_bloginfo() returns values.