Why Are My PDO Prepared Statements Failing to Insert Data into MySQL?

Troubleshooting PDO Prepared Statement Inserts in MySQL

Using PHP's PDO with MySQL prepared statements offers security and efficiency, but insertion issues can arise. This guide addresses a common problem: failed inserts despite seemingly correct code.

The Problem: Empty Database After an INSERT Attempt

Let's examine a scenario where an INSERT using a prepared statement doesn't populate the database:

$statement = $link->prepare("INSERT INTO testtable(name, lastname, age) VALUES('Bob','Desaunois','18')");
$statement->execute();

This code appears functional, yet the testtable remains empty.

The Solution: Parameter Binding

The solution involves correctly binding parameters. PDO prepared statements require placeholders—either named parameters (:param) or question marks (?)—within the SQL query. These placeholders are then populated with values during the execute() method.

Here's how to fix the code using both methods:

// Using Named Parameters
$statement = $link->prepare('INSERT INTO testtable (name, lastname, age) VALUES (:fname, :sname, :age)');
$statement->execute(['fname' => 'Bob', 'sname' => 'Desaunois', 'age' => '18']);

// Using Question Mark Placeholders
$statement = $link->prepare('INSERT INTO testtable (name, lastname, age) VALUES (?, ?, ?)');
$statement->execute(['Bob', 'Desaunois', '18']);

By utilizing parameter binding, you ensure data is safely inserted, mitigating SQL injection risks and maintaining data integrity. The values are correctly substituted into the query during execution.

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