PDOStatement::rowCount()

Also Known As

TL;DR

Explanation

rowCount() returns an integer reflecting rows modified by DML statements. For SELECT queries, the behaviour is driver-dependent — MySQL returns 0, making it unsuitable for counting result rows. Use SELECT COUNT(*) or fetchAll() + count() to count SELECT results. rowCount() is useful for detecting whether an UPDATE actually changed a row vs matched but left it unchanged.

Watch Out

Common Misconception

Why It Matters

Common Mistakes

• Using rowCount() to check if a SELECT found results — returns 0 on many drivers even with results.
• Expecting rowCount() to return rows matched — it returns rows changed. UPDATE with identical values returns 0.
• Not checking rowCount() after DELETE to confirm a row was actually removed.

Avoid When

• Never use rowCount() to check if a SELECT returned results — use fetch() === false or count(fetchAll()) instead.

When To Use

• Use after DELETE to verify a row was actually removed.
• Use after UPDATE to distinguish 'row not found' from 'row found but value unchanged'.

Code Examples

// Wrong — rowCount() on SELECT is not portable
$stmt = $pdo->prepare('SELECT * FROM users WHERE email = ?');
$stmt->execute([$email]);
if ($stmt->rowCount() > 0) { // unreliable — may return 0 even with results
    $user = $stmt->fetch();
}

// Correct: count SELECT results
$stmt = $pdo->prepare('SELECT * FROM users WHERE active = 1');
$stmt->execute();
$users = $stmt->fetchAll();
$count = count($users); // reliable

// Correct: check rows affected by UPDATE
$stmt = $pdo->prepare('UPDATE users SET last_seen = NOW() WHERE id = ?');
$stmt->execute([$userId]);
if ($stmt->rowCount() === 0) {
    // User not found or value unchanged
}

References

• ↗ https://www.php.net/manual/en/pdostatement.rowcount.php

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