Insert value in the list before or after the pivot value. the parameter options specify the position of the insert (before or after). If the list didn't exists, or the pivot didn't exists, the value is not inserted.
在指定LIST中的指定中枢VALUE的左侧或者右侧插入VALUE。如果这个LIST不存在，或者这个pivot(key position)不存在，那么这个VALUE不会被插入。
Parameters
key position Redis::BEFORE | Redis::AFTER pivot value
Return value
The number of the elements in the list, -1 if the pivot didn't exists.
Example
$redis->delete('key1');
$redis->lInsert('key1', Redis::AFTER, 'A', 'X'); /* 0 */
$redis->lPush('key1', 'A');
$redis->lPush('key1', 'B');
$redis->lPush('key1', 'C');
$redis->lInsert('key1', Redis::BEFORE, 'C', 'X'); /* 4 */
$redis->lRange('key1', 0, -1); /* array('A', 'B', 'X', 'C') */
$redis->lInsert('key1', Redis::AFTER, 'C', 'Y'); /* 5 */
$redis->lRange('key1', 0, -1); /* array('A', 'B', 'X', 'C', 'Y') */
$redis->lInsert('key1', Redis::AFTER, 'W', 'value'); /* -1 */
