src/Primitive/Container/Container.php
public function joinByKey($key, $glue = null)
    {
        return string(implode($glue, $this->lists($this->getKey($key))->all()));
    }
public function joinByKey($key, $glue = null)
    {
        return string(implode($glue, $this->lists($this->getKey($key))->all()));
    }
Concatenate values of a given key as a string.

@param mixed $key
@param null|mixed $glue
@return \im\Primitive\String\String