Code:
<?php
$result = "";
$fh = fopen( "http://127.0.0.1/manager/ispmgr?out=xml&func=user.edit&sok=yes&name=myname&passwd=topsecret&site=mydomain.com&access=mail&disklimit=10", "r" );
while( $data = fread( $fh, 4096 ) ){
$result .= $data;
}
fclose( $fh );
// After that the variable $result contains XML document with one node <ok/> or error codes and messages
?>
this document
http://ispsystem.com/docs/isp-lite-en-devel/index.html
describe all API functions and parameters.