php 使用php，如何在不覆盖文本文件开头的情况下插入文本

Using php, how to insert text without overwriting to the beginning of a text file

提问by ConroyP

I have:

我有：

<?php

$file=fopen(date("Y-m-d").".txt","r+") or exit("Unable to open file!");

if ($_POST["lastname"] <> "")
{
   fwrite($file,$_POST["lastname"]."\n");
}

fclose($file);

?>

but it overwrites the beginning of the file. How do I make it insert?

但它会覆盖文件的开头。我如何让它插入？

回答by ConroyP

I'm not entirely sure of your question - do you want to write data and not have it over-write the beginning of an existing file, or write new data to the start of an existing file, keeping the existing content after it?

我不完全确定您的问题 - 您想写入数据而不是覆盖现有文件的开头，还是将新数据写入现有文件的开头，并保留其后的现有内容？

To insert text without over-writing the beginning of the file, you'll have to open it for appending (a+rather than r+)

要在不覆盖文件开头的情况下插入文本，您必须打开它进行追加（a+而不是r+）

$file=fopen(date("Y-m-d").".txt","a+") or exit("Unable to open file!");

if ($_POST["lastname"] <> "")
{
   fwrite($file,$_POST["lastname"]."\n");
}

fclose($file);

If you're trying to write to the start of the file, you'll have to read in the file contents (see file_get_contents) first, then write your new string followed by file contents to the output file.

如果您尝试写入文件的开头，则必须先读入文件内容（请参阅 参考资料file_get_contents），然后将新字符串和文件内容写入输出文件。

$old_content = file_get_contents($file);
fwrite($file, $new_content."\n".$old_content);

The above approach will work with small files, but you may run into memory limits trying to read a large file in using file_get_conents. In this case, consider using rewind($file), which sets the file position indicator for handle to the beginning of the file stream. Note when using rewind(), not to open the file with the a(or a+) options, as:

上述方法适用于小文件，但在尝试使用file_get_conents. 在这种情况下，请考虑使用rewind($file)，它将句柄的文件位置指示符设置为文件流的开头。请注意，使用rewind(), 时不要使用a（或a+）选项打开文件，如：

If you have opened the file in append ("a" or "a+") mode, any data you write to the file will always be appended, regardless of the file position.

如果您以追加（“a”或“a+”）模式打开文件，则无论文件位置如何，您写入文件的任何数据都将始终被追加。

回答by oskarth

A working example for inserting in the middle of a file stream without overwriting, and without having to load the whole thing into a variable/memory:

一个在文件流中间插入而不覆盖的工作示例，无需将整个内容加载到变量/内存中：

function finsert($handle, $string, $bufferSize = 16384) {
    $insertionPoint = ftell($handle);

    // Create a temp file to stream into
    $tempPath = tempnam(sys_get_temp_dir(), "file-chainer");
    $lastPartHandle = fopen($tempPath, "w+");

    // Read in everything from the insertion point and forward
    while (!feof($handle)) {
        fwrite($lastPartHandle, fread($handle, $bufferSize), $bufferSize);
    }

    // Rewind to the insertion point
    fseek($handle, $insertionPoint);

    // Rewind the temporary stream
    rewind($lastPartHandle);

    // Write back everything starting with the string to insert
    fwrite($handle, $string);
    while (!feof($lastPartHandle)) {
        fwrite($handle, fread($lastPartHandle, $bufferSize), $bufferSize);
    }

    // Close the last part handle and delete it
    fclose($lastPartHandle);
    unlink($tempPath);

    // Re-set pointer
    fseek($handle, $insertionPoint + strlen($string));
}

$handle = fopen("file.txt", "w+");
fwrite($handle, "foobar");
rewind($handle);
finsert($handle, "baz");

// File stream is now: bazfoobar

Composer lib for it can be found here

可以在这里找到它的 Composer lib

回答by SeanDowney

If you want to put your text at the beginning of the file, you'd have to read the file contents first like:

如果要将文本放在文件的开头，则必须先阅读文件内容，例如：

<?php

$file=fopen(date("Y-m-d").".txt","r+") or exit("Unable to open file!");

if ($_POST["lastname"] <> "")
{    
    $existingText = file_get_contents($file);
    fwrite($file, $existingText . $_POST["lastname"]."\n");
}

fclose($file);

?>

回答by Eduardo Campa?ó

You get the same opening the file for appending

你同样可以打开文件进行追加

<?php
$file=fopen(date("Y-m-d").".txt","a+") or exit("Unable to open file!");
if ($_POST["lastname"] <> "")
{
   fwrite($file,$_POST["lastname"]."\n");
}
fclose($file);
?>