# pg_cancel_query

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

pg_cancel_query — 取消异步查询

### 说明

pg_cancel_query(PgSql\Connection `$connection`): bool

pg_cancel_query() 取消由 pg_send_query()、pg_send_query_params() 或 pg_send_execute() 发送的异步查询。不能取消使用 pg_query() 执行的查询。

### 参数

`connection`

  PgSql\Connection 实例。

### 返回值

成功时返回 `true`， 或者在失败时返回 `false`。

### 更新日志

版本 | 说明
--- | ---
8.1.0 | 现在 `connection` 参数接受 PgSql\Connection 实例，之前接受 resource。

### 示例

示例 #1 pg_cancel_query() 示例

`<?php
$dbconn = pg_connect("dbname=publisher") or die("Could not connect");
if (!pg_connection_busy($dbconn)) {
pg_send_query($dbconn, "select * from authors; select count(*) from authors;");
}
$res1 = pg_get_result($dbconn);
echo "First call to pg_get_result(): $res1\n";
$rows1 = pg_num_rows($res1);
echo "$res1 has $rows1 records\n\n";
// Cancel the currently running query. Will be the second query if it is
// still running.
pg_cancel_query($dbconn);
?>`

以上示例会输出：

    First call to pg_get_result(): Resource id #3
    Resource id #3 has 3 records

### 参见

- pg_send_query() - 发送异步查询
- pg_connection_busy() - 获取连接是否繁忙

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