How to overwrite a line if starts with a specific string in PHP?

Question

I have a text file, called logs.txt, I'm trying to create a script in PHP which is supposed to check if a string which starts with foo|| exists. If it exists, it should be replaced with a specific string, otherwise a specific string will be added at the end of the file.

This is the code I tried to make:

<?php

function replaceInFile($what, $with, $file){
    $buffer = "";
    $fp = file($file);
    foreach($fp as $line){
        $buffer .= preg_replace("|".$what."[A-Za-z_.]*|", $what.$with, $line);
    }
    fclose($fp);
    echo $buffer;
    file_put_contents($file, $buffer);
}

replaceInFile("foo||", "foo||hello", "logs.txt");

?>

but it doesn't really do what I want. Can someone help me on fixing the code? Any help is appreciated.

Look into fread() fwrite(). You're currently reading and writing the whole file, but not going through it line by line. when you find the line, you will want the pointer position so you can write to just that line. — CodingInTheUK, Oct 08 '17 at 01:35
@Chris an example is really appreciated too for a PHP beginner. :) — WayneXMayersX, Oct 08 '17 at 01:36
Possible duplicate of [Overwrite Line in File with PHP](https://stackoverflow.com/questions/235604/overwrite-line-in-file-with-php) — CodingInTheUK, Oct 08 '17 at 01:39
@Chris I'd like to look in a more elegant solution. I'll wait for other suggestions. And read better my question, it's a bit more different in this context, it's not a duplicate of that. :) — WayneXMayersX, Oct 08 '17 at 01:41

Webdesigner · Answer 1 · 2017-10-08T02:08:02.493

0

This should work:

$newline = preg_replace('/^' . $what . '(.*)$/', $with . '${1}', $line, 1 , $count);
$buffer .= ($count == 1) ? $newline : $line . $with;

The common Delimiters is / no | specially if you have | in your search criteria. Than you have to create a Capturing Group this is between ( and ). Now you can use this Capturing Group and in your replacement as ${ + number of the Capturing Group + }. In your case you only have one.

edited Oct 08 '17 at 02:08

answered Oct 08 '17 at 01:43

Webdesigner

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Will the specified string be added if no line starts with that string? – WayneXMayersX Oct 08 '17 at 01:45
Changed it to your needs. If we did a replace than we use it if not we use the original one with `$with` at the end. – Webdesigner Oct 08 '17 at 02:20

How to overwrite a line if starts with a specific string in PHP?

1 Answers1