Why Doesn't My PDO Prepared `INSERT INTO` Statement Work?

Troubleshooting PDO Prepared Statements for INSERT INTO in MySQL

Using PDO prepared statements for MySQL INSERT INTO operations can sometimes lead to unexpected results, such as no data being inserted. Let's examine a common cause and its solution.

Consider this code:

<code class="language-php">$statement = $link->prepare("INSERT INTO testtable(name, lastname, age)
        VALUES('Bob','Desaunois','18')");

$statement->execute();</code>

This code attempts to insert a new row into testtable, but often fails to populate the database.

The Missing Link: Parameter Binding

The problem lies in the absence of parameter binding. While prepared statements enhance security against SQL injection, they require you to use placeholders for values instead of directly embedding them in the query. This allows for safer and more efficient execution, especially when running the same query with multiple sets of data.

Solutions: Named and Positional Parameters

Here are two ways to correctly implement parameter binding:

1. Named Parameters:

<code class="language-php">$statement = $link->prepare('INSERT INTO testtable (name, lastname, age)
    VALUES (:fname, :sname, :age)');

$statement->execute([
    ':fname' => 'Bob',
    ':sname' => 'Desaunois',
    ':age' => '18',
]);</code>

This uses named placeholders (:fname, :sname, :age) that are mapped to values within the execute() method's array.

2. Positional Parameters:

<code class="language-php">$statement = $link->prepare('INSERT INTO testtable (name, lastname, age)
    VALUES (?, ?, ?)');

$statement->execute(['Bob', 'Desaunois', '18']);</code>

This employs question marks (?) as placeholders, with corresponding values provided in the execute() method's array. The order is crucial here.

Both approaches effectively bind parameters, preventing SQL injection and ensuring reliable data insertion. Choose the method that best suits your coding style and project requirements. Remember to always sanitize user inputs before using them in your queries, even with prepared statements, to maintain optimal security.

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