Topic awaiting preservation: how to cut a certain group of words in a string?

Hello there,
how to cut a certain group of words in a string, for example,
"<img src='images/smiles/grin.gif' smilietext=':grin:' border='0' style='vertical-align:middle' alt=':grin:' title=':grin:' />"
"<img src='images/smiles/smile.gif' smilietext=': smile:' border='0' style='vertical-align:middle' alt=': smile:' title=': smile:' />"
?..
from a forum comment.

I tried this:
$subject =$row_Recordset2['pagetext']
$pattern="/<img src='images\/smiles\/[a-zA-Z]+\.gif' smilietext=':[a-zA-Z]:' border='0' style='vertical-align:middle' alt=':[a-zA-Z]:' title=':[a-zA-Z]:' \/>/";
$result = preg_replace($pattern,"",$subject);
But I failed, I am new to PHP, please help. Thanks very much in advance.

logically, is it a better way to search for all what is inside the <img ... /> tag (including numbers) and replace them with ""?
I will write: $pattern="/<img [a-zA-Z][0-9]>\/>/", is it correct? Thank you for your help.

but what would you do with an empty <img>?
Please, explain again in detail: what do your strings look like before,
what should the look like after, and what information do you want to extract into seperate variables?
And can you have more than one occurance in a string?