Implementing API Filtering and Sorting

Map approved filter and sort fields to predetermined SQL expressions. The examples separate the essential operation from the conditions a production implementation must enforce.

What It Does

Map approved filter and sort fields to predetermined SQL expressions.

Prerequisites

Use a dedicated development environment with test accounts and records. Separate authorization, validation and error handling from response formatting; never copy demonstration-only secrets into production.

Example 1: Core Behavior

The first example isolates the core operation so its result is easy to understand.

<?php
$allowed=['name'=>'name','created'=>'created_at']; $requested=$_GET['sort']??'name';
$column=$allowed[$requested]??'name'; echo 'ORDER BY '.$column.' ASC';

Example 2: Alternative or Failure Case

The second example demonstrates an alternative outcome, rule or failure condition.

<?php
$direction=strtoupper((string)($_GET['direction']??'ASC'));
if (!in_array($direction,['ASC','DESC'],true)) $direction='ASC';
echo 'Sort direction: '.$direction;

Practical Example: Applying the Rule

The practical example shows how to carry the same constraint into application code.

<?php
$status=$_GET['status']??'active'; $allowed=['active','archived'];
if (!in_array($status,$allowed,true)) {http_response_code(422);exit;}
echo 'Use a prepared parameter for status: '.$status;

Important Behavior and Edge Cases

SQL parameter placeholders do not bind column names or ORDER BY directions.

Comparison with Related Functions or Patterns

Common Beginner Mistakes

Key Takeaways

• Map approved filter and sort fields to predetermined SQL expressions.
• SQL parameter placeholders do not bind column names or ORDER BY directions.
• Prepared values protect SQL literals while allowlists protect identifiers.

Select this API or pattern based on its documented behavior and the trust boundaries in your own application, and test all external integrations against their actual deployments.