PDO Named Placeholders

Also Known As

TL;DR

Explanation

Named placeholders use :name syntax and are bound by name in the execute() array (with or without the colon prefix). Unlike positional ?, named placeholders can be used in any order and reused multiple times in the same query. They are PDO-only — MySQLi does not support named placeholders. Named placeholders improve readability significantly in INSERT/UPDATE statements with many columns.

Common Misconception

Why It Matters

Common Mistakes

• Mixing named and positional placeholders in the same query — PDO does not support this.
• Forgetting that MySQLi only supports ? placeholders — named placeholders are PDO-only.
• Passing extra keys in the execute() array — PDO ignores them, but it signals a logic error.

Avoid When

• Do not mix named and positional placeholders in the same query — PDO will throw an error.
• Named placeholders are PDO-only — use positional ? when targeting MySQLi.

When To Use

• Use named placeholders for queries with 3+ parameters — greatly improves readability.
• Use named placeholders when the same value appears multiple times in the same query.

Code Examples

// Positional ? — hard to follow with many params
$stmt = $pdo->prepare('INSERT INTO users (email, name, role, created_at) VALUES (?, ?, ?, ?)');
$stmt->execute([$email, $name, 'user', date('Y-m-d H:i:s')]); // which ? is which?

// Named placeholders — readable for multi-column inserts
$stmt = $pdo->prepare(
    'INSERT INTO users (email, name, role, created_at)
     VALUES (:email, :name, :role, :created_at)'
);
$stmt->execute([
    ':email'      => $email,
    ':name'       => $name,
    ':role'       => 'user',
    ':created_at' => date('Y-m-d H:i:s'),
]);

// Reuse same placeholder
$stmt = $pdo->prepare('SELECT * FROM logs WHERE user_id = :uid OR created_by = :uid');
$stmt->execute([':uid' => $userId]);

References

• ↗ https://www.php.net/manual/en/pdo.prepare.php

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