Query parameters in Laravel

Introduction

Query parameters let you send extra information in a URL to control what data you get back. They help make your web app respond to user choices.

When filtering a list of products by category or price on an online store.

When searching for users by name or email in an admin panel.

When paginating results to show a specific page number.

When sorting data by date or popularity.

When passing optional settings or flags to a route.

Syntax

Laravel

use Illuminate\Http\Request;

Route::get('/search', function (Request $request) {
    $term = $request->query('term');
    // Use $term to filter results
});

Use $request->query('key') to get a query parameter value safely.

You can provide a default value like $request->query('key', 'default') if the parameter is missing.

Examples

This gets the 'category' parameter from the URL like ?category=books.

Laravel

use Illuminate\Http\Request;

Route::get('/products', function (Request $request) {
    $category = $request->query('category');
    return "Category: $category";
});

This gets the 'page' parameter or uses 1 if none is given.

Laravel

use Illuminate\Http\Request;

Route::get('/users', function (Request $request) {
    $page = $request->query('page', 1);
    return "Page number: $page";
});

This reads the search term from the URL query.

Laravel

use Illuminate\Http\Request;

Route::get('/search', function (Request $request) {
    $term = $request->query('term');
    return "Searching for: $term";
});

Sample Program

This route reads two query parameters, 'color' and 'size', and shows their values or defaults if missing.

Laravel

<?php

use Illuminate\Http\Request;
use Illuminate\Support\Facades\Route;

Route::get('/filter', function (Request $request) {
    $color = $request->query('color', 'any');
    $size = $request->query('size', 'all');
    return "Filter applied: color=$color, size=$size";
});

Important Notes

Query parameters are part of the URL after the ? symbol, like ?color=red&size=large.

Always validate or sanitize query parameters before using them to avoid security issues.

Laravel's Request object makes it easy to access query parameters with query().

Summary

Query parameters send extra info in URLs to control data returned.

Use $request->query('key') to get them in Laravel routes.

Provide default values to handle missing parameters gracefully.

Practice

1. What is the purpose of query parameters in a Laravel application URL?

easy

A. To define the database schema

B. To style the webpage with CSS

C. To send extra information to control the data returned by the server

D. To store user session data on the server

Solution

1. Step 1: Understand what query parameters do

   Query parameters are parts of the URL that send extra info to the server, usually after a question mark.

2. Step 2: Identify their use in Laravel

   In Laravel, query parameters help control what data the server returns based on the extra info sent.

3. Final Answer:

   To send extra information to control the data returned by the server -> Option C

4. Quick Check:

   Query parameters control returned data = B [OK]

Hint: Query parameters add info after ? in URL to filter data [OK]

Common Mistakes:

• Confusing query parameters with database schema
• Thinking query parameters style the page
• Assuming query parameters store session data

2. Which is the correct Laravel syntax to get a query parameter named page from a request?

easy

A. $request->param('page')

B. $request->input('page')

C. $request->getQuery('page')

D. $request->query('page')

Solution

1. Step 1: Recall Laravel method for query parameters

   Laravel uses $request->query('key') to get query parameters from the URL.

2. Step 2: Match the correct syntax

   Among options, only $request->query('page') correctly accesses the query parameter named 'page'.

3. Final Answer:

   $request->query('page') -> Option D

4. Quick Check:

   Use $request->query('key') for query params = A [OK]

Hint: Use $request->query('key') to get query params in Laravel [OK]

Common Mistakes:

• Using $request->input() which also works but includes POST data
• Using non-existent methods like getQuery or param
• Confusing query() with input() for query parameters

3. Given this Laravel route code:

Route::get('/search', function (Request $request) {
    $term = $request->query('term', 'default');
    return $term;
});

What will be the output if the URL is /search?term=laravel?

medium

A. laravel

B. default

C. null

D. term

Solution

1. Step 1: Understand query parameter retrieval with default

   The code uses $request->query('term', 'default'), which returns the 'term' parameter if present, else 'default'.

2. Step 2: Check the URL query parameter

   The URL has ?term=laravel, so 'term' is 'laravel', not missing.

3. Final Answer:

   laravel -> Option A

4. Quick Check:

   Query param 'term' present = 'laravel' [OK]

Hint: If query param exists, default is ignored [OK]

Common Mistakes:

• Assuming default value is always returned
• Confusing parameter name with its value
• Expecting null when parameter is present

4. Identify the error in this Laravel code snippet that tries to get a query parameter sort:

Route::get('/items', function (Request $request) {
    $sort = $request->query['sort'];
    return $sort;
});

medium

A. Request class not imported

B. Using array syntax instead of method call for query parameters

C. Incorrect route method; should be post() instead of get()

D. Missing semicolon after return statement

Solution

1. Step 1: Check how query parameters are accessed

   The code uses $request->query['sort'], which is incorrect because query is a method, not an array.

2. Step 2: Correct syntax for query parameters

   The correct way is $request->query('sort') to get the 'sort' parameter.

3. Final Answer:

   Using array syntax instead of method call for query parameters -> Option B

4. Quick Check:

   Use $request->query('key'), not $request->query['key'] [OK]

Hint: query() is a method, not an array; use parentheses [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Confusing get() with query() method
• Assuming query is a property, not a method

5. You want to get a query parameter filter in Laravel but provide a default value of all if it is missing or empty. Which code correctly handles this?

hard

A. $filter = $request->query('filter') ?: 'all';

B. $filter = $request->input('filter', 'all');

C. $filter = $request->query('filter', 'all');

D. $filter = $request->query('filter') ?? 'all';

Solution

1. Step 1: Understand default value behavior in query()

   The second argument in query('filter', 'all') returns 'all' only if the parameter is missing, but not if empty.

2. Step 2: Handle empty values as well

   Using $request->query('filter') ?: 'all' returns 'all' if the parameter is missing or empty (falsy).

3. Step 3: Check other options

   $filter = $request->input('filter', 'all'); uses input() which includes POST data, not just query. $filter = $request->query('filter') ?? 'all'; uses null coalescing which does not treat empty string as missing.

4. Final Answer:

   $filter = $request->query('filter') ?: 'all'; -> Option A

5. Quick Check:

   Use ?: to handle missing or empty query params = C [OK]

Hint: Use ?: to cover missing or empty query parameters [OK]

Common Mistakes:

• Assuming default in query() covers empty strings
• Using input() which mixes POST and query data
• Using ?? which ignores empty strings