Is there a PHP function for imploding an associative array without losing the keys?

The title of this question is self-explanatory.

I've heard I can mimic this using http_build_query, but I'd rather use a function that's meant for this.

Input example:

$assoc = array(
    "fruit" => "banana",
    "berry" => "blurberry",
    "vegetable" => "lettice"
);

Desired output (I get this with http_build_query):

string(46) "fruit=banana,berry=blurberry,vegeta开发者_Python百科ble=lettice"

output from reversal wanted is the same as input - that's my current problem.

Implode with

serialize($array);

Explode with

unserialize($array);

Found a function in the php .net comments for implode:

function implode_with_key($glue = null, $pieces, $hifen = ',') {
    $return = null;
    foreach ($pieces as $tk => $tv) $return .= $glue.$tk.$hifen.$tv;
    return substr($return,1);
}