Replacing a [shortcode] with a query from the database

Before you send the text to domPDF you can loop through the allowed placeholders and replace the text with data from the database.

$placeHolders = ['[company_name]' => $company->name, '[company_address]' => $company->address, '[company_email]' => $company->email];
foreach($placeHolders AS $placeholder => $replaceWith){
    $documentText = str_replace($placeholder, $replaceWith, $documentText);
}
// Send $documentText to domPDF.
// ...

Aha, I see - that's great, thanks @steinmagne. Is this to work with the webwizo shortcodes package I referenced or is there another way I should do it?

This is not for webwizo package. I would create a new class that handles this. Example below. I have also added possibility to chain if you have different type of data to be replaced. Haven't tested this very much so there may be some bugs :) But you can give it a try.

namespace App\core;
use App\Company;
use App\Other;
use vendor\Dompdf\Dompdf; // or wherever it may live

class Placeholder{

    private static $documentText;
    private static $_instance = null;

    public static function load($documentText){
        if (self::$_instance === null) {
            self::$_instance = new self;
        }
        self::$documentText = $documentText;
        return self::$_instance;
    }

    public function replaceCompany($companyId = 1){
        // default value 1 for testing purposes
        // Get company
        $company = Company::whereId($companyId)->first();
        // Define placeholders
        $placeHolders = [
            '[company_name]' => $company->customer_name,
            '[company_address]' => $company->address,
            '[company_email]' => $company->email
        ];
        foreach($placeHolders AS $placeholder => $replaceWith){
            static::$documentText = str_replace($placeholder, $replaceWith, static::$documentText);
        }
        return $this;
    }
    public function replaceOther($otherId = 1){
        // default value 1 for testing purposes. This model is the same as company, just different name to show how it can be done.
        // Get Other
        $other = Other::whereId($otherId)->first();
        // Define placeholders
        $placeHolders = [
            '[zip_code]' => $other->zipcode,
            '[city]' => $other->city
        ];
        foreach($placeHolders AS $placeholder => $replaceWith){
            static::$documentText = str_replace($placeholder, $replaceWith, static::$documentText);
        }
        return $this;
    }

    public function get(){
        return static::$documentText;
    }
}

// Use it
// Get documentdata.
$document = ['content' => 'Company name : [company_name]. Address: [company_address], [zip_code] [city].'];

// Replace text with chaining
$documentText = Placeholder::load($document['content'])->replaceCompany()->replaceOther()->get();

$dompdf = new Dompdf();
$dompdf->loadHtml($documentText);
$dompdf->render();
$dompdf->stream();

You don’t need to do replacements in a foreach() loop. The str_replace() function accepts array for the first two arguments, so you could do this:

$shortcodes = [
    '[company_name]' => $company->customer_name,
    '[company_address]' => $company->address,
    '[company_email]' => $company->email,
    // and so on
];

$find = array_keys($shortcodes);
$replace = array_values($shortcodes);

$string = str_replace($find, $replace, $string);

Thanks so much chaps, I'll give the above a try and see how I get on (if all works well I'll mark this question as answered).