need help for .... ereg_replace ... to replace number

[humax9110]

hello every body,

I want to replce the number (between 7 to 11 digit) to (U can't post number) by using ereg_replace

I made this

$message = ereg_replace('[0-9]{7,11}','(u can't post number)',$message);

but this will replace all number even that 1234678.gif or 12345678.jpg

what I want that to replace only sprate number Neither *12345678 nor 12345678* mean if there is char. before or after number not replace the number ....

Thanks ...