Help with this script

[rkm140]

I am changing certain text to images that fall within these brackets [ ].

THe problem i am having is that sometime it will replace the text and sometimes it won't, also it is changing the text that matches even if it isn't within the brackets.
How can i fix this to work how it needs to.

$cards = array('2','3','4','5','6','7','8','9','T','J','Q','K','A');
$suits = array ('c','d','h','s');

$fromArray = $toArray = array();
foreach($cards as $card) {
   foreach($suits as $suit) {
      $word[] = '['.$card.$suit;
      $word[] = $card.$suit.']';
      $word[] = ' '.$card.$suit.' ';
      $link[] = '[<img src="http://mypokerrails.com/forum1/cards/'.$card.$suit.'.png">';
      $link[] = '<img src="http://mypokerrails.com/forum1/cards/'.$card.$suit.'.png">]';
      $link[] = '<img src="http://mypokerrails.com/forum1/cards/'.$card.$suit.'.png">';
   }
}
$this->post['message'] = str_ireplace($word, $link, $this->post['message']);