How can undefined variable errors be avoided when querying databases in PHP?

To avoid undefined variable errors when querying databases in PHP, you should always check if the variable is set before using it. This can be done using the isset() function to determine if a variable is set and is not NULL. By checking if the variable is set before using it in your query, you can prevent undefined variable errors from occurring. 

// Check if the variable is set before using it in the query
if(isset($variable)){
    // Use the variable in your query
    $query = "SELECT * FROM table WHERE column = '$variable'";
    // Execute the query
    $result = mysqli_query($connection, $query);
}

Keywords

PHP database querying error handling isset function variable declaration

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