PHP PDOStatement::fetchColumn Tutorial
last modified April 19, 2025
The PDOStatement::fetchColumn method in PHP retrieves a single column from the next row of a result set. It's efficient for getting scalar values.
Basic Definition
PDOStatement::fetchColumn returns a single column from the next row of a result set. It moves the internal pointer forward after fetching.
Syntax: public PDOStatement::fetchColumn(int $column = 0): mixed.
The optional parameter specifies which column to return (0-indexed).
Fetching a Single Column Value
This example demonstrates fetching a single value from the first column.
<?php
declare(strict_types=1);
try {
$pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $pdo->query('SELECT COUNT(*) FROM users');
$count = $stmt->fetchColumn();
echo "Total users: $count";
} catch (PDOException $e) {
echo "Error: " . $e->getMessage();
}
This counts all users in the database. fetchColumn returns the first column from the first row of the result set. It's perfect for aggregate functions.
Fetching Specific Column
This shows how to fetch a specific column by its index.
<?php
declare(strict_types=1);
try {
$pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $pdo->query('SELECT id, name, email FROM users LIMIT 1');
$email = $stmt->fetchColumn(2);
echo "User email: $email";
} catch (PDOException $e) {
echo "Error: " . $e->getMessage();
}
This fetches the email (third column, index 2) from the first user. Column indexing starts at 0. The method returns false if no more rows exist.
Looping Through a Column
This demonstrates iterating through all values in a single column.
<?php
declare(strict_types=1);
try {
$pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $pdo->query('SELECT name FROM users');
echo "User names:\n";
while ($name = $stmt->fetchColumn()) {
echo "- $name\n";
}
} catch (PDOException $e) {
echo "Error: " . $e->getMessage();
}
This loops through all names in the users table. Each fetchColumn call moves to the next row. The loop ends when fetchColumn returns false.
With Prepared Statements
This shows fetchColumn used with prepared statements.
<?php
declare(strict_types=1);
try {
$pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $pdo->prepare('SELECT email FROM users WHERE id = ?');
$stmt->execute([42]);
$email = $stmt->fetchColumn();
if ($email !== false) {
echo "User email: $email";
} else {
echo "User not found";
}
} catch (PDOException $e) {
echo "Error: " . $e->getMessage();
}
This safely fetches an email using a prepared statement. We check for false to handle cases where no user matches the ID. Always validate the return value.
Fetching Multiple Columns
This demonstrates how to fetch different columns sequentially.
<?php
declare(strict_types=1);
try {
$pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $pdo->query('SELECT name, email, created_at FROM users LIMIT 1');
$name = $stmt->fetchColumn(0);
$email = $stmt->fetchColumn(1);
$date = $stmt->fetchColumn(2);
echo "Name: $name, Email: $email, Joined: $date";
} catch (PDOException $e) {
echo "Error: " . $e->getMessage();
}
This fetches three different columns from the same row. Each fetchColumn call advances the row pointer, so this approach only works for single-row results. For multiple rows, use fetch() instead.
Handling NULL Values
This shows how fetchColumn handles NULL database values.
<?php
declare(strict_types=1);
try {
$pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $pdo->query('SELECT middle_name FROM users WHERE id = 1');
$middleName = $stmt->fetchColumn();
if ($middleName === false) {
echo "User not found";
} elseif ($middleName === null) {
echo "No middle name specified";
} else {
echo "Middle name: $middleName";
}
} catch (PDOException $e) {
echo "Error: " . $e->getMessage();
}
This demonstrates NULL handling. A NULL database value returns as PHP null. A missing row returns false. Always check both possibilities when working with nullable columns.
Performance Comparison
This compares fetchColumn with fetch for single-column retrieval.
<?php
declare(strict_types=1);
try {
$pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
// Using fetch
$start = microtime(true);
$stmt = $pdo->query('SELECT name FROM users');
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
$name = $row['name'];
}
$fetchTime = microtime(true) - $start;
// Using fetchColumn
$start = microtime(true);
$stmt = $pdo->query('SELECT name FROM users');
while ($name = $stmt->fetchColumn()) {
// Just getting the name
}
$fetchColumnTime = microtime(true) - $start;
echo "Fetch time: $fetchTime\n";
echo "fetchColumn time: $fetchColumnTime";
} catch (PDOException $e) {
echo "Error: " . $e->getMessage();
}
This benchmarks both methods. fetchColumn is slightly faster for single-column retrieval as it avoids creating associative arrays. The difference becomes noticeable with large result sets.
Best Practices
- Column Index: Always specify when not using first column.
- NULL Handling: Check for both false and null returns.
- Single Column: Use only when you need one column.
- Performance: Prefer for large single-column results.
- Error Checking: Always verify the return value.
Source
This tutorial covered the PDOStatement::fetchColumn method with
practical examples showing various usage scenarios and best practices.
Author
List all PHP PDO Functions.