What are the best practices for determining the appropriate scale for the vertical axis in a bar chart created with PHP?

When determining the appropriate scale for the vertical axis in a bar chart created with PHP, it is important to consider the range of data values being displayed. The scale should be chosen to clearly represent the data without distorting the visual representation of the bars. One common approach is to calculate the maximum value of the data and then round it up to the nearest "friendly" number, such as a multiple of 5 or 10.

// Sample data values
$data = [15, 22, 30, 45, 55];

// Calculate the maximum value in the data
$max_value = max($data);

// Round up the maximum value to the nearest friendly number
$scale = ceil($max_value / 10) * 10;

// Use $scale as the maximum value for the vertical axis in the bar chart