What are the potential pitfalls of using htmlspecialchars() for both field names and field values in SQL queries in PHP?

When using htmlspecialchars() for both field names and field values in SQL queries in PHP, the potential pitfall is that it may cause unexpected behavior or errors in the query execution. To solve this issue, it is recommended to only use htmlspecialchars() for user-inputted field values to prevent SQL injection attacks, and not for field names as they are not user-controlled. 

// Example of using htmlspecialchars() only for field values and not for field names in an SQL query
$field_name = "user_input"; // Field name not sanitized
$field_value = htmlspecialchars($_POST['user_input']); // Field value sanitized

$sql = "SELECT * FROM table_name WHERE $field_name = '$field_value'";
$result = mysqli_query($connection, $sql);

// Rest of the code handling the query result

Keywords

htmlspecialchars SQL injection security vulnerability data sanitization escaping characters

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