<?php
$id = 248;
$sTest = "247(text goes here)248(more here)";
preg_match("/\b" . $id . "\(([^\)]*)\)/", $sTest, $aMatches); $sResult = $aMatches[1];
echo $sResult;
PD9waHAKCiRpZCA9IDI0ODsKJHNUZXN0ID0gIjI0Nyh0ZXh0IGdvZXMgaGVyZSkyNDgobW9yZSBoZXJlKSI7CnByZWdfbWF0Y2goIi9cYiIgLiAkaWQgLiAiXCgoW15cKV0qKVwpLyIsICRzVGVzdCwgJGFNYXRjaGVzKTsKJHNSZXN1bHQgPSAkYU1hdGNoZXNbMV07CmVjaG8gJHNSZXN1bHQ7