<?php
$string = "somerandomcharacters[code]object1[/code]somerandomcharacters[code]object2[/code]somerandomcharacters[code]object3[/code]somerandomcharacters";
preg_match_all('%\[code\](.*?)\[/code\]%i', $string, $matches, PREG_PATTERN_ORDER
);
PD9waHAKCiRzdHJpbmcgPSAic29tZXJhbmRvbWNoYXJhY3RlcnNbY29kZV1vYmplY3QxWy9jb2RlXXNvbWVyYW5kb21jaGFyYWN0ZXJzW2NvZGVdb2JqZWN0MlsvY29kZV1zb21lcmFuZG9tY2hhcmFjdGVyc1tjb2RlXW9iamVjdDNbL2NvZGVdc29tZXJhbmRvbWNoYXJhY3RlcnMiOwoKcHJlZ19tYXRjaF9hbGwoJyVcW2NvZGVcXSguKj8pXFsvY29kZVxdJWknLCAkc3RyaW5nLCAkbWF0Y2hlcywgUFJFR19QQVRURVJOX09SREVSKTsKCnByaW50X3IoJG1hdGNoZXNbMV0pOw==