LARAVEL. Scripts goes through all .php and .blade.php files and looks for missing translation keys and adds it to the en.json file. If there are some non-used translations in en.json file they will be deleted.

ExtractTranslationsCommand.php

<?php

namespace App\Console\Commands;

use Illuminate\Console\Command;
use RecursiveDirectoryIterator;
use RecursiveIteratorIterator;
use RecursiveRegexIterator;
use RegexIterator;

class ExtractTranslationsCommand extends Command
{
    /**
     * The name and signature of the console command.
     *
     * @var string
     */
    protected $signature = 'app:extract-translations-command';

    /**
     * The console command description.
     *
     * @var string
     */
    protected $description = 'Extract translations from files and add it to .json file';

    private string $phpDir;
    private string $bladeDir;
    private string $jsonFile;
    private int $numberOfRemovedTranslations = 0;
    private int $numberOfAddedTranslations = 0;

    public function handle()
    {
        $this->phpDir = base_path() . '/app';
        $this->bladeDir = base_path() . '/resources/views';
        $this->jsonFile = base_path() . '/lang/en.json';

        $phpFiles = $this->getFiles($this->phpDir);
        $bladeFiles = $this->getFiles($this->bladeDir);

        $phpStrings = $this->extractStringsFromFiles($phpFiles);
        $bladeStrings = $this->extractStringsFromFiles($bladeFiles);

        $allStrings = array_merge($phpStrings, $bladeStrings);

        $this->insertIntoJson($allStrings, $this->jsonFile);
        $this->removeFromJson($allStrings, $this->jsonFile);

        $this->info("Strings inserted into {$this->jsonFile} successfully.");
        $this->info('Number of added translations: ' . $this->numberOfAddedTranslations);
        $this->info('Number of removed translations: ' . $this->numberOfRemovedTranslations);
    }

    private function getFiles($dir)
    {
        $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($dir));
        $regexIterator = new RegexIterator(
            $iterator, '/^.+\.php$|^.+\.blade\.php$/i', RecursiveRegexIterator::GET_MATCH
        );

        $files = [];
        foreach ($regexIterator as $file) {
            $files[] = $file[0];
        }

        return $files;
    }

    private function extractStringsFromFiles($files)
    {
        $strings = [];
        $patterns = ["/__\('(.*?)'\)/", "/trans_choice\('([^']+)',/"];

        foreach ($patterns as $pattern) {
            foreach ($files as $file) {
                $content = file_get_contents($file);
                if (preg_match_all($pattern, $content, $matches)) {
                    $strings = array_merge($strings, $matches[1]);
                }
            }
        }
        
        return $strings;
    }

    private function insertIntoJson(array $strings, string $jsonFile)
    {
        $existingData = [];
        if (file_exists($jsonFile)) {
            $existingData = json_decode(file_get_contents($jsonFile), true);
        }

        foreach ($strings as $string) {
            if (!array_key_exists($string, $existingData)) {
                $existingData[$string] = $string;
                $this->numberOfAddedTranslations++;
            }
        }

        ksort($existingData);
        file_put_contents($jsonFile, json_encode($existingData, JSON_PRETTY_PRINT));
    }

    private function removeFromJson(array $strings, string $jsonFile): void
    {
        $existingData = [];
        if (file_exists($jsonFile)) {
            $existingData = json_decode(file_get_contents($jsonFile), true);
        }

        foreach ($existingData as $stringKey => $stringValue) {
            if (!in_array($stringKey, $strings)) {
                unset($existingData[$stringKey]);
                $this->numberOfRemovedTranslations++;
            }
        }

        ksort($existingData);
        file_put_contents($jsonFile, json_encode($existingData, JSON_PRETTY_PRINT));
    }
}