Returns the number of columns in the current result set.
The objective is to understand the behavior and operational limits, not only the method name.
What It Does
Returns the number of columns in the current result set.
Syntax and Return Value
PDOStatement::columnCount(): mixedThe return value and exceptional cases depend on the call described here: It is not the number of rows, and availability of metadata depends on execution and driver.
Example 1: Basic Use
The statement has a real query and result set; database-specific metadata and statement options may be unsupported.
<?php
$pdo = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$pdo->exec('CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT NOT NULL, price INTEGER NOT NULL, active INTEGER)');
$pdo->exec("INSERT INTO products (id,name,price,active) VALUES (1,'Desk',120,1),(2,'Lamp',35,1),(3,'Chair',85,0)");
$stmt = $pdo->query("SELECT id, name, price FROM products LIMIT 1");
echo $stmt->columnCount();Example 2: A Second Scenario
The statement has a real query and result set; database-specific metadata and statement options may be unsupported. This additional check distinguishes the method's result from connection or statement state.
<?php
$pdo = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$pdo->exec('CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT NOT NULL, price INTEGER NOT NULL, active INTEGER)');
$pdo->exec("INSERT INTO products (id,name,price,active) VALUES (1,'Desk',120,1),(2,'Lamp',35,1),(3,'Chair',85,0)");
$stmt = $pdo->query("SELECT id, name, price FROM products LIMIT 1");
echo $stmt->columnCount();
echo $stmt->columnCount() === 3 ? "three columns" : "different shape";Example 3: Practical Checks
The statement has a real query and result set; database-specific metadata and statement options may be unsupported. This additional check distinguishes the method's result from connection or statement state.
<?php
$pdo = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$pdo->exec('CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT NOT NULL, price INTEGER NOT NULL, active INTEGER)');
$pdo->exec("INSERT INTO products (id,name,price,active) VALUES (1,'Desk',120,1),(2,'Lamp',35,1),(3,'Chair',85,0)");
$stmt = $pdo->query("SELECT id, name, price FROM products LIMIT 1");
echo $stmt->columnCount();
echo "Result columns: " . $stmt->columnCount();Important Behavior and Edge Cases
It is not the number of rows, and availability of metadata depends on execution and driver.
For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.
Comparison with Related Approaches
| Approach | Important distinction |
|---|---|
| PDOStatement::columnCount | Returns the number of columns in the current result set. |
| Related API / pattern | rowCount is intended chiefly for affected rows, not portable SELECT counts. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Assuming the happy path covers edge cases | It is not the number of rows, and availability of metadata depends on execution and driver. |
| Using a related API interchangeably | rowCount is intended chiefly for affected rows, not portable SELECT counts. |
Key Takeaways
- Returns the number of columns in the current result set.
- It is not the number of rows, and availability of metadata depends on execution and driver.
- rowCount is intended chiefly for affected rows, not portable SELECT counts.
Choose this API or pattern when its exact semantics match your task, and verify the result against the database driver and runtime used by your application.