In php, a string is inserted at the last 140 bytes of the file, but the file pointer is always at the end of the file.

{Code ...} I want to ask why I have used fseek to change the file pointer to the last 140 bytes, but it is still written at the end of the file. If so, why? What is a reasonable idea?

  ';$handle = fopen("D:/wamp/www/liuyanban.html","a"); fseek($handle, -140,SEEK_END); fwrite($handle, "ok"); fclose($handle);?>

I want to ask why I have used fseek to change the file pointer to the last 140 bytes, but it is still written at the end of the file. If so, why? What is a reasonable idea?

Reply content:

  ';$handle = fopen("D:/wamp/www/liuyanban.html","a"); fseek($handle, -140,SEEK_END); fwrite($handle, "ok"); fclose($handle);?>

I want to ask why I have used fseek to change the file pointer to the last 140 bytes, but it is still written at the end of the file. If so, why? What is a reasonable idea?

File Opening Methodr+.

Http://php.net/manual/zh/function.fopen.php

'R' is opened in read-only mode. It directs the file pointer to the file header. Open in 'r + 'read/write mode and point the file pointer to the file header. Open in 'W' writing mode, point the file pointer to the file header, and cut the file size to zero. If the file does not exist, try to create it. Open in 'W + 'read/write mode, point the file pointer to the file header, and cut the file size to zero. If the file does not exist, try to create it. Open the 'A' write mode and point the file pointer to the end of the file. If the file does not exist, try to create it. Open in 'a + 'read/write mode and point the file pointer to the end of the file. If the file does not exist, try to create it.

Aboutfseek.
Http://php.net/manual/zh/function.fseek.php

Note: If you use the attached mode (a or a +), any data written to the file will be appended, and the file location will be ignored. Call fseek () the result is not defined yet.

The result is that the specified character is written at the specified position, but the insert effect is not achieved.
To achieve the insert effect, you need to first jump to the specified location, get all the content behind it, then write the content you want to write, and then write the original content.