Mass assignment protection in Laravel - Step-by-Step Execution

Concept Flow - Mass assignment protection

Receive user input data

↓

Attempt to create/update model with input

↓

Check model's fillable or guarded properties for each field

↓

Allow assignment

↓

Save model

↓

End process

This flow shows how Laravel checks if input data can be assigned to model fields safely, blocking any unallowed fields to protect data.

Execution Sample

Laravel

User::create(['name' => 'Ana', 'role' => 'admin']);

// In User model:
// protected $fillable = ['name'];

This code tries to create a user with name and role, but only 'name' is allowed to be mass assigned.

Execution Table

Step	Action	Input Data	Model fillable	Allowed Fields	Blocked Fields	Result
1	Receive input	{name: 'Ana', role: 'admin'}	['name']	name	role	Proceed to assign
2	Check each input field	name	['name']	Allowed	-	Assign 'Ana' to name
3	Check each input field	role	['name']	-	Blocked	Prevent assignment of 'role'
4	Create model instance	-	-	name	-	Model created with name='Ana' only
5	Save model	-	-	-	-	User saved in database
6	End	-	-	-	-	Process complete, no mass assignment error

💡 Mass assignment blocked for 'role' field because it is not in fillable array

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
inputData	{name: 'Ana', role: 'admin'}	{name: 'Ana', role: 'admin'}	{name: 'Ana', role: 'admin'}	{name: 'Ana', role: 'admin'}
fillable	[]	['name']	['name']	['name']
allowedFields	[]	['name']	['name']	['name']
blockedFields	[]	[]	['role']	['role']
modelAttributes	{}	{name: 'Ana'}	{name: 'Ana'}	{name: 'Ana'}

Key Moments - 2 Insights

Why is the 'role' field not saved even though it was in the input?

Because 'role' is not listed in the model's fillable array, Laravel blocks it to prevent mass assignment. See execution_table step 3 where 'role' is blocked.

What happens if the fillable array is empty?

No fields are allowed for mass assignment, so any attempt to assign input data will be blocked, resulting in no attributes being mass assigned. This is shown by the blockedFields tracking in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution table, which field is blocked from assignment?

A both name and role

B name

C role

D none

💡 Hint

Check the 'Blocked Fields' column in execution_table row 3

At which step is the model instance created with allowed fields?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at the 'Result' column in execution_table row 4

If 'role' was added to fillable, what would change in the execution table?

A 'role' would be allowed and assigned at step 3

B 'role' would still be blocked

C Model creation would fail

D Input data would be empty

💡 Hint

Compare 'fillable' and 'blockedFields' columns in execution_table rows 2 and 3

Concept Snapshot

Mass assignment protection in Laravel:
- Use $fillable array in model to list allowed fields
- Input fields not in $fillable are blocked
- Prevents accidental or malicious data overwrite
- Silently ignores blocked fields
- Always define $fillable or $guarded to secure models

Full Transcript

Mass assignment protection in Laravel helps keep your app safe by controlling which input fields can be assigned to your model all at once. When you try to create or update a model using an array of data, Laravel checks the model's fillable array. Only fields listed there are allowed to be assigned. Others are blocked to prevent unwanted changes. For example, if you try to assign 'name' and 'role' but only 'name' is fillable, Laravel will assign 'name' and block 'role'. This stops users from changing sensitive fields like roles or permissions by accident or attack. The process ends with the model saved with only allowed fields. Always set fillable or guarded properties in your models to keep mass assignment safe.