The PHP client library defines the following error codes and constants. These can be used against the return value for most operations to determine whether they succeeded, or failed, and in the event of a failure, what the underlying cause was. The constants are distributed between both generic interface errors, and operation specific errors. Check the corresponding API call tables for information on which errors are raised by each operation.

You can use the getResultCode() and getResultMessage() methods to obtain the error code and message for each operation. You can use these in combination with the error constants to determine a specific course of action when an operation fails, for example:

$cb->replace("fork", "Hello World!", 10);

if ($cb->getResultCode() === COUCHBASE_KEY_ENOENT) {
  // Doesn't exist, add it first                                                                                                        
  $cb->add("fork", "Hello World!", 10);
  echo "Key added (didn't exist)\n";
} elseif ($cb->getResultCode() === SUCCESS) {
  echo "Key updated\n";
} else {
  echo "Error occurred: ", $cb->getResultMessage(), "<br/>";
}

In the above example, an update operation is attempted on a key which must already exist. If Couchbase Server returns an error that the key didn't exist, add() is used to create the key. If the operation was successful, we output a success message. For all other errors, the error message is generated.

The getResultCode() and getResultMessage() return the error from the previous API call.

A full list of the constants and error messages available for each operation as shown in Table 3.2, “PHP Error Codes and Constants”.