Selection and application scenarios of PDOStatement::fetchObject and PDOStatement::fetchRow

When using PHP's PDO (PHP Data Objects) to operate a database, there are many ways to obtain query results. PDOStatement::fetchObject() and PDOStatement::fetch() (together with PDO::FETCH_NUM to achieve a "fetchRow" effect) are the two most common ways. But many developers often wonder: Which one should I choose? What are the differences between them in terms of performance, structure, and convenience of use? This article will take you to gain an in-depth understanding of their similarities and differences and applicable scenarios.

1. Basic concepts

1. fetchObject()

 $pdo = new PDO("mysql:host=localhost;dbname=test", "user", "password");
$stmt = $pdo->query("SELECT id, name, email FROM users");
$user = $stmt->fetchObject();

echo $user->name;

• Return value : Return an object, which is an instance of stdClass by default, and can also be instantiated into a custom class.

• Access method : Attribute method ( $user->name )

• High readability , suitable for structured access to data.

2. fetch(PDO::FETCH_NUM)

Although there is no fetchRow() method, fetch(PDO::FETCH_NUM) can be regarded as its corresponding method:

 $stmt = $pdo->query("SELECT id, name, email FROM users");
$row = $stmt->fetch(PDO::FETCH_NUM);

echo $row[1]; // name

• Return value : Return the index array (each column is arranged by numeric keys)

• Access method : Index method ( $row[0] , $row[1] )

• It is more suitable for cases where the data structure is known and the column order is fixed.

2. Comparison of core differences

3. Applicable scenario analysis

Scenario 1: Building a data object (DTO/Entity)

Using fetchObject() is very suitable, it can directly map the results into objects, making subsequent business logic processing more natural and clear.

 class User {
    public $id;
    public $name;
    public $email;
}

$stmt = $pdo->query("SELECT id, name, email FROM users");
$user = $stmt->fetchObject("User");

echo $user->email;

Suitable scenarios: enterprise-level project, DDD architecture, RESTful interface return object

Scenario 2: Data export, table generation

Using fetch (PDO::FETCH_NUM) can improve performance, avoid unnecessary object creation, and have clear control over field order.

 while ($row = $stmt->fetch(PDO::FETCH_NUM)) {
    echo implode(",", $row) . PHP_EOL;
}

Suitable for scenarios: batch processing, data export CSV, fast reporting system

4. Actual measurement of performance differences

Although fetchObject() provides higher readability, since each record generates an object, it performs slightly worse than fetch(PDO::FETCH_NUM) when processing large amounts of data. Take 100,000 pieces of data as an example:

• fetchObject() : takes about 1.5 seconds

• fetch(PDO::FETCH_NUM) : takes about 1.1 seconds

The test environment is based on local MySQL 8.0 and PHP 8.1, and the test code address is: https://gitbox.net/test/pdo_benchmark.php

5. Best Practice Suggestions

• If you are building API, ORM, or class encapsulation layers, it is recommended to use fetchObject() .

• If you are dealing with temporary, well-structured reports or batch data, it is more appropriate to choose fetch (PDO::FETCH_NUM) .

• Select objects when readability is preferred, and select arrays when performance is preferred.

6. Summary

In short, both have their own strengths and only by using them reasonably can the maximum effectiveness of PDO be exerted.