PHP How to overwrite a specific section of a file

Question

I have a small CSS file.

:root {
    --header-bg:
#004d73;
    --header-title-color:
#dbebfa;
}

I am trying to write a script that accepts an input value and overwrites a specific line in the CSS file with the new data. Here is what I have so far.

 $path = 'custom-test.css';
 if (isset($_POST['header-bg'])) {
    $fh = fopen($path,"a+");
    $string = $_POST['header-bg'];
    fwrite($fh,$string,7); // Write information to the file
    fclose($fh); // Close the file
    header('Location: ' . $_SERVER['HTTP_REFERER']);
 }

This is working, except of course it simply appends the data to the end of the file.

I can't figure out if I need to specify what line to overwrite through fopen, fwrite, or if I need the script to open the entire file into an array (which is way beyond my rudimentary PHP skillset).

Again, my skills are quite limited. All tips are welcome, but suggestions that expand upon my existing code would be very helpful.

BTW without going into detail I cannot use a database entry for this.

Answer 1

The best and standard way to do that is making a template file and then render that file with parameters.
Take a look at this

First make a template file like this :

:root {
    --header-bg: <?=$this->e($headerBg)?>;
    --header-title-color: <?=$this->e($headerTitleColor)?>;
}

and in your php script:

 $path = './';
 $template = 'custom-test.css';
 $output = 'output-test.css';
 if (isset($_POST['header-bg'])) {
    $params = [
        'headerBg' => $_POST['header-bg'],
        'headerTitleColor' => ''
    ];
    $templates = new League\Plates\Engine($path);
    file_put_content($output, $templates->render($template, $params));
    header('Location: ' . $_SERVER['HTTP_REFERER']);
 }

You must install this package with composer (if you are using composer) :

composer require league/plates

And then import it in your script require 'vendor/autoload.php'
If you don't use composer you must download it and include below files in your script

    "src/Template/match.php",
    "src/Extension/Data/data.php",
    "src/Extension/Path/path.php",
    "src/Extension/RenderContext/func.php",
    "src/Extension/RenderContext/render-context.php",
    "src/Extension/LayoutSections/layout-sections.php",
    "src/Extension/Folders/folders.php",
    "src/Util/util.php"

Answer 2

You can use a template file, and str_replace function and do it like this.

Let's assume you have style.css which contains this :

:root {
    --header-bg: #004d73;
    --header-title-color: #dbebfa;
}

and you have template.style.css which contains this :

:root {
    --header-bg: {{background}};
    --header-title-color: {{color}};
}

Now all you have to do whenever you need to change style.css is replace the values in template.style.css and place the content in style.css

<?php 

$background = $_POST['background'];
$color      = $_POST['color'];
// you may need to check these values before using them

$contents = file_get_contents('template.style.css');
$css = str_replace('{{background}}',$background,$contents);
$css = str_replace('{{color}}',$color,$css);
file_put_contents('style.css',$css);



?>

Update

From your comments, I understand that you are trying to use different theme color for each website you have in different servers, and you don't need php for that.

The simplest method is to change each file manually for each website since you are not going to change them again, but! if you want something more dynamic, still you don't need php, because in that cause you are going to need Less.js: using 2 variables in your less file (you don't need to change CSS, you only need to replace the colors by variable name @varName) and set the variable via less.js for each website.

Update

In your situation I think the first answer is the best, I'll leave my second suggestion in case someone was looking for that answer or found it useful in a different situation.