function smiley($str){
//smileys to check for
$smiles=array(
":)",":-)",":D",":-D",";)",";-)",":O",
":-O",":P",":-P","w00t","8)","8-)",":S",
":s","\:\(","\;\(","\|\)",":@"
);
// replace with emoticons
$replacements=array(
"<img src="http//yourwebsite.com/image/smile.gif" width="20" height="20" title="happy smiley" />",
"<img src="http//yourwebsite.com/image/smile.gif" width="20" height="20" title="happy smiley" />",
"<img src="http//yourwebsite.com/image/biggrin.gif" width="20" height="20" title="big grin smiley" />",
"<img src="http//yourwebsite.com/image/biggrin.gif" width="20" height="20" title="big grin smiley" />",
"<img src="http//yourwebsite.com/image/wink.gif" width="20" height="20" title="winking smiley" />",
"<img src="http//yourwebsite.com/image/wink.gif" width="20" height="20" title="winking smiley" />",
"<img src="http//yourwebsite.com/image/ohmy.gif" width="20" height="20" title="oh my smiley" />",
"<img src="http//yourwebsite.com/image/ohmy.gif" width="20" height="20" title="oh my smiley" />",
"<img src="http//yourwebsite.com/image/tongue.gif" width="20" height="20" title="tongue smiley" />",
"<img src="http//yourwebsite.com/image/tongue.gif" width="20" height="20" title="tongue smiley" />",
"<img src="http//yourwebsite.com/image/w00t.gif" width="20" height="20" title="w00t smiley" />",
"<img src="http//yourwebsite.com/image/roll.gif" width="20" height="20" title="roll eyes smiley" />",
"<img src="http//yourwebsite.com/image/roll.gif" width="20" height="20" title="roll eyes smiley" />",
"<img src="http//yourwebsite.com/image/huh.gif" width="20" height="20" title="huh smiley" />",
"<img src="http//yourwebsite.com/image/huh.gif" width="20" height="20" title="huh smiley" />",
"<img src="http//yourwebsite.com/image/sad.gif" width="20" height="20" title="sad smiley" />",
"<img src="http//yourwebsite.com/image/crying.gif" width="20" height="20" title="crying smiley" />",
"<img src="http//yourwebsite.com/image/sleep.gif" width="20" height="20" title="sleep smiley" />",
"<img src="http//yourwebsite.com/image/mad.gif" width="20" height="20" title="mad smiley" />",
);
for($i=0;$i < sizeof($smiles);$i++){
$str=eregi_replace($smiles[$i], $replacements[$i], strtolower($str));
}
return $str;
}

Emoticons :) to Image

PHP