Laravel 5: Use implode() with Eloquent the right way
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
# Laravel 5: Use `implode()` with Eloquent the Right Way – Beyond Simple String Concatenation
As a senior developer, I often encounter scenarios where developers try to force relational data into simple string formats for database storage. The problem you've encountered—trying to use `implode()` on an array from a request and facing type errors during saving—highlights a common pitfall: confusing *data transformation* with *database modeling*.
While using `implode()` seems like a quick fix to get data into a single column, it often sacrifices the relational integrity that Laravel and Eloquent are designed to handle beautifully. This post will explore why this approach is problematic and demonstrate the truly idiomatic, powerful way to manage many-to-many relationships in a Laravel application.
## The Pitfall of String Implosion
You are attempting to take an array of checkbox values (e.g., `[1, 2, 3]`) and convert it into a string (`"1,2,3"`) before saving it to a single column. While technically possible with PHP's `implode()`, this method has significant drawbacks:
1. **Loss of Relationship:** The database no longer knows that the values `1`, `2`, and `3` belong to a specific set of items; they are just arbitrary text in a string field.
2. **Query Inefficiency:** You cannot easily query or filter based on these individual selections later without complex, slow string manipulation within your SQL queries.
3. **Data Integrity Risk:** If you ever need to retrieve the data, you must manually split the string back into an array, which is error-prone.
The error you saw (`strtolower() expects parameter 1 to be string, array given`) likely occurred because somewhere in your saving logic, you were attempting a function that expected a single string but received the raw array from the request, indicating a mismatch between what the database field expects and what PHP functions expect as input during the save process.
## Solution 1: The Quick Fix (If You Must Store as CSV)
If, for some legacy reason or specific reporting need, you absolutely must store these values as a single delimited string in one column, here is how you perform the transformation correctly within your controller. This method is generally discouraged for complex data structures, but it solves the immediate requirement:
```php
use Illuminate\Http\Request;
use App\Models\YourModel; // Assuming you have a model
class YourController extends Controller
{
public function store(Request $request)
{
// 1. Get the array of selected IDs from the request
$extraServices = $request->input('extra_services', []);
// 2. Use implode() to create the desired string format (e.g., "1,2,3")
$serviceString = implode(',', $extraServices);
// 3. Save the single string to the database column
YourModel::create([
'some_data' => $request->currency,
'service_list' => $serviceString, // Storing as a string
]);
return redirect()->back()->with('success', 'Data saved successfully.');
}
}
```