How can missing quotation marks in SQL queries impact the functionality of data updates in PHP?

Missing quotation marks in SQL queries can lead to syntax errors, especially when dealing with string values. This can prevent data updates from being executed properly in PHP. To solve this issue, always ensure that string values in SQL queries are enclosed in quotation marks.

// Incorrect SQL query without quotation marks
$sql = "UPDATE users SET name = $name WHERE id = $id";

// Corrected SQL query with quotation marks
$sql = "UPDATE users SET name = '$name' WHERE id = $id";