How can mixing INSERT and UPDATE syntax in PHP code affect the functionality of transferring form data to a database?

Mixing INSERT and UPDATE syntax in PHP code can lead to unexpected behavior when transferring form data to a database. It can result in duplicate entries being inserted or incorrect updates being made to existing records. To solve this issue, it's important to determine whether to insert a new record or update an existing one based on the data being submitted. 

// Check if the record already exists in the database
$sql = "SELECT * FROM table_name WHERE id = :id";
$stmt = $pdo->prepare($sql);
$stmt->execute(['id' => $id]);
$row = $stmt->fetch();

if ($row) {
    // Update existing record
    $sql = "UPDATE table_name SET column1 = :value1, column2 = :value2 WHERE id = :id";
} else {
    // Insert new record
    $sql = "INSERT INTO table_name (column1, column2) VALUES (:value1, :value2)";
}

$stmt = $pdo->prepare($sql);
$stmt->execute(['value1' => $value1, 'value2' => $value2, 'id' => $id]);

Keywords

INSERT UPDATE syntax PHP code database transfer

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