$value = array('key1'=>'value1','key2'=>'value2','key3'=>'value3');

key1=value1&key2=value2&key3=value3

implode($value,"&"); // returns value1&value2&value3

$value = array('key1'=>'value1','key2'=>'value2','key3'=>'value3');

echo http_build_query($value); // key1=value1&key2=value2&key3=value3