Copies data from one stream to another

# stream_copy_to_stream

(PHP 5, PHP 7, PHP 8)

stream_copy_to_stream — Copies data from one stream to another

### 说明

function stream_copy_to_stream(
resource `$from`,
resource `$to`,
?int `$length` = `null`,
int `$offset` = 0
): int|false

Makes a copy of up to `length` bytes of data from the current position (or from the `offset` position, if specified) in `from` to `to`. If `length` is `null`, all remaining content in `from` will be copied.

### 参数

`from`

  The source stream

`to`

  The destination stream

`length`

  Maximum bytes to copy. By default all bytes left are copied.

`offset`

  The offset where to start to copy data

### 返回值

Returns the total count of bytes copied, 或者在失败时返回 `false`.

### 更新日志

版本 | 说明
--- | ---
8.0.0 | `length` is now nullable.

### 示例

示例 #1 A stream_copy_to_stream() example

    <?php
    $src = fopen('http://www.example.com', 'r');
    $dest1 = fopen('first1k.txt', 'w');
    $dest2 = fopen('remainder.txt', 'w');

    echo stream_copy_to_stream($src, $dest1, 1024) . " bytes copied to first1k.txt\n";
    echo stream_copy_to_stream($src, $dest2) . " bytes copied to remainder.txt\n";

    ?>

### 参见

- copy() - 拷贝文件

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