Load Laravel eloquent attribute by string

Question

I am storing some strings in my database, and I want to be able to get model attributes using them.

Basically, I can call a users booking like this

$user->bookings->date

in my controller and it works, and i'm storing a string in my database like this

'user->bookings->date'

How can I use this string from the database to get the attribute? I'm hoping to be able to do something like

$user = User::findOrFail(1);
$string = 'user->bookings->date'; //This is fetched from the db normally
$booking_date = ${$string}; //Instead of writing $user->bookings->date

Is this possible?

Won't exactly work like that, as the object accessor -> needs to be outside of {} to work properly. i.e. something like ${$string1}->{$string2}->{$string3}; would work, but I'm not sure how to construct that dynamically. — Tim Lewis
– Tim Lewis, Commented Jun 18, 2019 at 16:15

Tim Lewis · Accepted Answer · 2019-06-18 16:20:00Z

2

I've found a solution that involves chaining object access from a static string:

$user = User::findOrFail(1);

$string = "user->bookings->date";
$params = explode("->", $string);

$var = null;
foreach($params AS $param){
    if($var){
        $var = $var->{$param};
    } else {
        $var = ${$param};
    }
}

dd($var);

On the first iteration of $params, set $var to the value of ${$param} ($user). Then, on the next iterations, set $var to the value of $var->{$param} ($user->bookings, $user->bookings->date). Then, finally, echo out (or dd()) the value of $var. In my test, this results in

"2019-06-18 12:06:00"

So while it requires a bit of additional logic, it is possible to set object access from a database string.

answered Jun 18, 2019 at 16:20

Tim Lewis

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3 Comments

S_R Over a year ago

This looks good, I've managed to find a method using the eval function, but every fibre of my being screams at me to not use it, just incase.

Tim Lewis Over a year ago

Yeah... eval() can be great when you know you will have absolute control of what's being evaluated, but performing it on something that can change a lot is a terrible idea :P

S_R Over a year ago

Yup, i'm not going to allow my users to type in a string, the string that is stored will be built dynamically, to avoid anyone simply typing $user->delete() or something.

dlogon · Accepted Answer · 2023-08-09 01:49:06Z

0

You can use Arr::get helper method

With this, you can use "dot notation". So you should change the '->' with '.' and the 'user.' with ''

$string = "user->bookings->date";
$field = str_replace("->", ".", $string);
$field = str_replace("user.", "", $field);
// We want the string "bookings.date"

$user = User::findOrFail(1);

Arr::get($user, $field, "default value")

With this, you can go deeper as you need, and this returns you a single column or a collection if you have hasMany relation

answered Aug 9, 2023 at 1:49

dlogon

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