Sets whether this cursor will be left open after fetching the last results

# MongoCursor::tailable

(PECL mongo >=0.9.4)

MongoCursor::tailable — Sets whether this cursor will be left open after fetching the last results

### 説明

public MongoCursor::tailable ([ bool `$tail` = `TRUE` ] ) : MongoCursor

Mongo has a feature known as tailable cursors which are similar to the Unix "tail -f" command.

Tailable means cursor is not closed when the last data is retrieved. Rather, the cursor marks the final object's position. you can resume using the cursor later, from where it was located, if more data were received.

Like any "latent cursor", the cursor may become invalid at some point -- for example if that final object it references were deleted. Thus, you should be prepared to requery if the cursor is MongoCursor::dead().

### パラメータ

`tail`

  If the cursor should be tailable.

### 返り値

Returns this cursor.

### エラー / 例外

Throws MongoCursorException if this cursor has started iterating.

### 例

例1 MongoCursor::tailable() example

`<?php
$cursor = $collection->find()->tailable();
$results = array();
while (1) {
if (!$cursor->hasNext()) {
// we've read all the results, exit
if ($cursor->dead()) {
break;
}
// read all results so far, wait for more
sleep(10);
}
else {
$results[] = $cursor->getNext();
}
}
?>`

### 参考

MongoDB core docs on » tailable cursors.

- MongoCursor::awaitData() - Sets whether this cursor will wait for a while for a tailable cursor to return more data