What are the limitations of input and output values in neural networks when using PHP?

When working with neural networks in PHP, one limitation to be aware of is the range of input and output values. Neural networks typically work best with input values between 0 and 1, and output values can also be constrained to this range for better performance. To ensure that your input and output values fall within this range, you can normalize your data before training and predicting with the neural network.

// Normalize input data to be between 0 and 1
function normalizeInput($input_data) {
    $min = min($input_data);
    $max = max($input_data);
    
    return array_map(function($value) use ($min, $max) {
        return ($value - $min) / ($max - $min);
    }, $input_data);
}

// Normalize output data to be between 0 and 1
function normalizeOutput($output_data) {
    $min = min($output_data);
    $max = max($output_data);
    
    return array_map(function($value) use ($min, $max) {
        return ($value - $min) / ($max - $min);
    }, $output_data);
}

// Example usage
$input_data = [2, 5, 8];
$output_data = [10, 20, 30];

$normalized_input = normalizeInput($input_data);
$normalized_output = normalizeOutput($output_data);

print_r($normalized_input);
print_r($normalized_output);