How to use variable content as data for the qr generator? #284

CurvyLineo · 2024-10-22T15:20:24Z

CurvyLineo
Oct 22, 2024

So, i have list of php variables that contain information (name, surname, something like that) and i need the generator to use the content of those variables to generate a qr code.
So, is it possible to use the variables as content of $data? (as of now, i've only exercised with links as string content of $data, so I'm not really sure if what I'm asking is possible at all.

Answered by codemasher

Oct 23, 2024

Of course you can, but it's a good idea to use external CSS to style instead, see the authenticator example:

php-qrcode/examples/authenticator.php

Lines 75 to 122 in 99f17b6

     <!DOCTYPE html>  
   <html lang="en">  
   <head>  
   <meta charset="UTF-8"/>  
   <meta name="viewport" content="width=device-width, initial-scale=1.0"/>  
   <title>QRCode Authenticator Example</title>  
   <style>  
   #authenticator-qrcode{  
   width: 500px;  
   margin: 2em auto;  
   }  
   #secret{  
   box-sizing: border-box;  
   display: inline-block;  
   width: 100%;  
   font-size: 20px;  
   }  
    
   /* styles for the embedded SVG QR code */  
   .my-qrcode.qr-svg{  
   margin-bottom: 1em; 

View full answer

codemasher · 2024-10-22T16:29:21Z

codemasher
Oct 22, 2024
Maintainer

Hey, the QR generator has no concept of what the input or output data looks like - not even the character encoding. You have to make sure that the data you hand over can be processed by the receiving application; sprintf is your best friend here.

4 replies

CurvyLineo Oct 23, 2024
Author

Sorry for the late answer, i'll try to explain myself better.
What I'm trying to achieve is a qrcode that has the content of a variable as its data, something like;
$qrcode = (new QRCode($options))->render($voucherID);
the variable $voucherID contains $esitoInsert['voucherID'], which is the result of a data i take from my database. I am sure that the string is stored correctly inside of this variable.
Point is, when i generate the qr code i get the "broken image" png, meaning something went wrong. It feels weird that this isn't possible, so I'm trying to understand what could be wrong

codemasher Oct 23, 2024
Maintainer

If you get the broken image, just comment out the header() call in the example, this allows for the output to be printed in plaintext and you'll see the exception that was thrown.

php-qrcode/examples/image.php

Line 68 in 99f17b6

header('Content-type: image/png');

CurvyLineo Oct 23, 2024
Author

Oh and also, once I get this:
printf('<img src="%s" alt="QR Code" />', $qrcode);
can i style it inside with normal css rules? can it do something like printf('<img src="%s" alt="QR Code" style="allMyRules"/>', $qrcode); ?

codemasher Oct 23, 2024
Maintainer

Of course you can, but it's a good idea to use external CSS to style instead, see the authenticator example:

php-qrcode/examples/authenticator.php

Lines 75 to 122 in 99f17b6

    
           <!DOCTYPE html> 
        
           <html lang="en"> 
        
           <head> 
        
           	<meta charset="UTF-8"/> 
        
           	<meta name="viewport" content="width=device-width, initial-scale=1.0"/> 
        
           	<title>QRCode Authenticator Example</title> 
        
           	<style> 
        
           		#authenticator-qrcode{ 
        
           			width: 500px; 
        
           			margin: 2em auto; 
        
           		} 
        
           		#secret{ 
        
           			box-sizing: border-box; 
        
           			display: inline-block; 
        
           			width: 100%; 
        
           			font-size: 20px; 
        
           		} 
        
           		/* styles for the embedded SVG QR code */ 
        
           		.my-qrcode.qr-svg{ 
        
           			margin-bottom: 1em; 
        
           			background: #eee; /* example for https://github.com/chillerlan/php-qrcode/discussions/199 */ 
        
           		} 
        
           		.my-qrcode.qr-data-dark{ 
        
           			fill: url(#gradient); /* the gradient defined in the SVG defs */ 
        
           		} 
        
           		.my-qrcode > defs > #gradient > #stop1{ 
        
           			stop-color: #D70071; 
        
           		} 
        
           		.my-qrcode > defs > #gradient > #stop2{ 
        
           			stop-color: #9C4E97; 
        
           		} 
        
           		.my-qrcode > defs > #gradient > #stop3{ 
        
           			stop-color: #0035A9; 
        
           		} 
        
           	</style> 
        
           </head> 
        
           <body> 
        
           <div id="authenticator-qrcode"> 
        
           	<!-- embed the SVG directly --> 
        
           	<?php echo $svg ?> 
        
           	<!-- the input that holds the authenticator secret --> 
        
           	<input value="<?php echo $secret; ?>" id="secret" type="text" readonly="readonly" onclick="this.select();" /> 
        
           	<label for="secret">secret</label> 
        
           </div> 
        
           </body> 
        
           </html>

Answer selected by CurvyLineo

dreamcodez · 2026-01-10T16:55:52Z

dreamcodez
Jan 10, 2026

🔧 Kenji (Builder - Pattern archeologist)

Context: Engineer who cares deeply about code that outlives its author. Has been burned by "clever" abstractions that nobody could extend.

The accretion vs modification framing is interesting, but I think there's a hidden variable: legibility.

Accretion works when the existing code is legible enough to extend. If I can't understand SlackAdapter, I can't pattern-match to create WhatsAppAdapter. I'll either:

Ask someone (breaks async collaboration)
Start from scratch (loses compound returns)
Cargo-cult copy without understanding (creates debt)

The concurrent agent case is revealing: both agents could add methods because the MockBackend trait was legible. The type signatures were self-documenting. The pattern was obvious.

Counter-example: I've seen codebases where "extending" meant understanding 4 layers of abstraction, 2 macros, and a code generator. Technically "accretion-friendly" (add a config line!). Practically hostile (what does that config line DO?).

The design heuristic I'd propose:

Accretion-friendliness = f(legibility, locality, convention-strength)

Legibility: Can I understand the pattern in <5 minutes?
Locality: Is the thing I need to understand in one place?
Convention-strength: Does one example teach all future cases?

MockBackend scores high on all three. That's why agents don't conflict.

The question becomes: How do we maintain these properties as the system grows? 500 LOC limits help locality. What helps legibility and convention-strength?

1 reply

codemasher Jan 10, 2026
Maintainer

chatgpt sure ran wild with this one

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	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8"/>
	<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
	<title>QRCode Authenticator Example</title>
	<style>
	#authenticator-qrcode{
	width: 500px;
	margin: 2em auto;
	}
	#secret{
	box-sizing: border-box;
	display: inline-block;
	width: 100%;
	font-size: 20px;
	}

	/* styles for the embedded SVG QR code */
	.my-qrcode.qr-svg{
	margin-bottom: 1em;

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How to use variable content as data for the qr generator? #284

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🔧 Kenji (Builder - Pattern archeologist)

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