fwrite writing from beginning without removing

问题

I am using PHP and fwrite code, but I want every write position to start from the beginning of the file without erasing it's content. I am using this code but it is writing to the end of the file.

$fr = fopen("aaaa.txt", "a");
fwrite($fr, "text");
fclose($fr);

回答1:

So you want to write at the beginning of a file, leaving all of its current contents after the new data? You'll have to grab its existing contents first, then append it back into the file once you've overwritten with your new data.

$file = 'aaaa.txt';
$oldContents = file_get_contents($file);
$fr = fopen($file, 'w');
fwrite($fr, "text");
fwrite($fr, $oldContents);
fclose($fr);

If you want to avoid loading the original file's contents into memory in your PHP script, you might try first writing to a temp file, using a loop buffer or system calls to append the contents of your original file to the temp file, then remove the original file and rename your temp file.

回答2:

From the PHP site:

Note:

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

I suggest something like this (from php.net site):

$handle = fopen('output.txt', 'r+');

fwrite($handle, 'Really long sentence.');
rewind($handle);
fwrite($handle, 'Foo');
rewind($handle);

echo fread($handle, filesize('output.txt'));

fclose($handle);

回答3:

$file = 'aaaa.txt';
$tmp = file_get_contents($file);
$tmp = 'text'.$tmp;
$tmp = file_put_contents($file, $tmp);
echo ($tmp != false)? 'OK': '!OK';

回答4:

use this code :

$file = 'aaaa.txt';
$oldContents = file_get_contents($file);
$fr = fopen($file, 'w');
$newmsg="text".$oldContents;
fwrite($fr, $oldContents);
fclose($fr);

回答5:

Prefetching old content with file_get_contents and appending it after writing new content is one way to do it. But In case, the file is being dynamically written and along the way you needed to go back to the beginning of file and add some text, then here is how:

$handle = fopen($FILE_PATH, 'w+');
fwrite($handle, "I am writing to a new empty file 
                and now I need to add Hello World to the beginning");

to prepend Hello World do the following:

$oldText = '';
fseek($handle, 0);
while (!feof($handle)) {
   $oldText .= fgets($handle);
}
fseek($handle, 0);
fwrite($handle, "Hello World! ");
fwrite($handle, $oldText);

fclose($handle);

The result would be:

Hello World! I am writing to a new empty file and now I need to add Hello World to the beginning

Reminder and like Fabrizio already noted:

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

回答6:

This should work:

$file="name.extension";
$current = file_get_contents($file);
$user = $_POST["username"];
$pass = $_POST["password"];
file_put_contents($file,$current . "Whatever you want to add here"

This finds the current stuff and copy/pastes it back each time the code is ran (tried to make it as simple as possible in case other answers are a little too complicated)

回答7:

Open a file in w+ mode not a+ mode.
Get the length of text to add ($chunkLength)
set a file cursor to the beginning of the file
read $chunkLength bytes from the file
return the cursor to the $chunkLength * $i;
write $prepend
set $prepend a value from step 4

do these steps, while EOF

$handler = fopen('1.txt', 'w+');//1
rewind($handler);//3
$prepend = "I would like to add this text to the beginning of this file";
$chunkLength = strlen($prepend);//2
$i = 0;
do{
    $readData = fread($handler, $chunkLength);//4
    fseek($handler, $i * $chunkLength);//5
    fwrite($handler, $prepend);//6

    $prepend = $readData;//7
    $i++;
}while ($readData);//8

fclose($handler);

回答8:

Use fseek() to set your position in the file.

$fr = fopen("aaaa.txt", "r+");
fseek($fr, 0); // this line will set the position to the beginning of the file
fwrite($fr, "text");
fclose($fr);

来源：https://stackoverflow.com/questions/6681221/fwrite-writing-from-beginning-without-removing

标签

php

fwrite