Add content to a specific location in txt

Answer 1

The following are some ways to add content to specific locations in txts:

** 1. Add content at the end of the document **
1. Use the `file_put_contents` function
- The basic usage is `file_put_contents(filepath,data, CHARACTEREND)`. For example:
```php
$data = "What to add";
file_put_contents('test.txt',$data,FILE_APPEND);
```
2. First read the contents of the file, then write it after modifying it.
- You can use `file_get_contents` to read the entire file content into a string, then connect the additional content to the string and write it in with `file_put_contents`.
```php
$content = file_get_contents('test.txt');
$appendData = "What to add";
$newContent = $content.$ appendData;
file_put_contents('test.txt',$newContent);
```

** 2. Add content to a specific line in the middle of the file (external commands such as sed can be used. This method is relatively complicated and may require the support of a specific server environment)**
1. If you are in a Linux-based server environment, you can use the `sed` command.(Although this is not a pure PhP-based method, it can be called through functions such as `exec'.)
- For example, if you want to add something after a matching line (let's say it's a line that contains the string 'toxingwang.com'), you can use:
```php
//Assuming that in a linux-based environment, the following code calls the sed command in PHP
$command = 'sed -i'/toxingwang.com/a' additional content 'test.txt';
exec($command);
```
- The `a` here means to add content after the matching line. If you want to add content before the matching line, you can replace `a` with `i`(you need to pay attention to the escape characters in actual use).

- If you want to add content based on the line number (assuming you add content after the fourth line), you can use:
```php
$command = 'sed -i'4a 'added content' test.txt';
exec($command);
```
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