simple regular exp question

[cash_hr]

what code i have to type to get whole word from the text with eregi_replace.

from $buffer i am ripping a part of text, but with -->
$buffer_rez= "... ".substr($buffer, $_pos-100,200)." ...";

i cant get whole words at star and end.

now i need to ereg_replace buffer one more with condition that first and last character must be blank space.

I was thinking something like:
$buffer_rez=eregi_replace($buffer_rez,'^{[[:blank:]]$',$buffer_rez);}

please help quick

thanks