如何通过PHP重写文件的特定值？

Question

<?php
  $info = "Hi";
  $file = fopen("file.txt","w");
  fwrite($file,$info);
  fclose($file);
?> 

I am currently using the code above to write a value into a text file. However, is it possible to retrieve certain variables that are stored within that text file and just rewrite them instead?

Example:

file.txt

$one = "first";
$two = "second";
$three = "third";

Through PHP code, a specified "variable" in the text file should have its contents changed.

New file.txt

$one = "first";
$two = "hi";
$three = "third";

Answer 1

If I understand you correctly, you have some PHP code written in a file, file.txt. If you have only stored variables, I believe you can get away with some regular expression to do what you want.

Nevertheless, for anything more complex (maybe even for this specific case), I would recommend that you use some PHP parser to parse all the variables and their values, and make your changes accordingly. (here's a PHP parser written in PHP).

EDIT:

Just to clear things up, a simple replacement will not suffice. Imagine you have something like $first = "a";, and then you decide to replace a, with \. A naive replacement, would leave you with $first = "\"; in your file.txt file.