Laravel use string from MySQL as variable - php

Question

Good night, I have a code that substitutes the data from the request and displays it, like this:
$client = User::find($data['$id']);
$execute = 'Send command ';
$execute .= $client->id;
dd($execute);
It return
^ "Send command 1"
Everything is working.
But I want that if I add a variable to the database, for example, like this
$client->id
, and call it, then I need the code to process it as a variable, and not as a string, how to do this, thanks)
Example:
(inside the variable $cliend in the database will be the following code:
$client->id
Code:
$client = DB::table('users')->where('id', $id)->value('id');
$execute = 'Send command ';
$execute .= $client;
dd($execute);
It is necessary that this variable be executed as a variable. and returned its value not from the database, but as in the first example

Answer 1

Having to store variable names into the database is extremely bad practice although PHP does natively support variables variable.
In your case, I do not see how you could implement this against an object without having to eval some additional code against, assumingly, untrusted user input.
I would first suggest redesigning your database logic to avoid this but if this is necessary or/and your data is controlled then here is a solution:
// Your object you want to access the value of
$client = (object) ['id' => 1];
// Data from your SQL statement that stores that variable name
$databaseValue = '$client->id';
// Eval and store result as variable
eval("\$value = {$databaseValue};");
// Result: Send command 1
echo "Send command {$value}";
See it working over at 3v4l.org
Some additional thoughts, you could potentially use regex to capture that the stored data is indeed a variable and only grab the first match.
^\$(?:[a-z]||[A-Z])\S+
You can see an example of this over on 3v4l.org where we remove any potential bad stuff from the data but this is a very blacklisted approach and you should always look to take a whitelisted approach. Just hoping this helps down the line somewhere else.
For some explanation, please checkout regex101 where I added some examples how this could be easily escaped and is no way the ultimate solution.
Update: Here is another regex you could potentially use to narrow down this even further.
(?:\s|^)\$(?:[^\s]+?)(?:[a-z])+(?:->|$)?(?:[a-z]|[A-Z])+
Example and explanation can be found over at Regex101. PHP example can be found over at 3v4l.org (which remember is still never perfect).