如何在PHP中使用Oracle数据库的并发控制和锁机制

<?php
// 连接Oracle数据库
$conn = oci_connect('username', 'password', 'database');

// 查询需要更新的数据并锁定
$query = "SELECT * FROM my_table WHERE id = :id FOR UPDATE";
$stmt = oci_parse($conn, $query);
$id = 1;
oci_bind_by_name($stmt, ':id', $id);
oci_execute($stmt);

// 更新数据
$query = "UPDATE my_table SET field = :field WHERE id = :id";
$stmt = oci_parse($conn, $query);
$field = 'new value';
oci_bind_by_name($stmt, ':field', $field);
oci_bind_by_name($stmt, ':id', $id);
oci_execute($stmt);

// 提交事务并关闭连接
oci_commit($conn);
oci_close($conn);
?>

<?php
// 连接Oracle数据库
$conn = oci_connect('username', 'password', 'database');

// 查询数据并获取版本信息
$query = "SELECT * FROM my_table WHERE id = :id";
$stmt = oci_parse($conn, $query);
$id = 1;
oci_bind_by_name($stmt, ':id', $id);
oci_execute($stmt);
$row = oci_fetch_array($stmt, OCI_ASSOC);
$oldVersion = $row['VERSION'];

// 更新数据
$newVersion = $oldVersion + 1;
$query = "UPDATE my_table SET field = :field, version = :newVersion WHERE id = :id AND version = :oldVersion";
$stmt = oci_parse($conn, $query);
$field = 'new value';
oci_bind_by_name($stmt, ':field', $field);
oci_bind_by_name($stmt, ':newVersion', $newVersion);
oci_bind_by_name($stmt, ':id', $id);
oci_bind_by_name($stmt, ':oldVersion', $oldVersion);
oci_execute($stmt);

// 检查更新行数
if (oci_num_rows($stmt) == 0) {
    // 更新失败，数据已被修改
    oci_rollback($conn);
} else {
    // 更新成功
    oci_commit($conn);
}

// 关闭连接
oci_close($conn);
?>