Backward and forward unit converter

backward_forward_unit_converter.php

<?php

// Function to convert a value from one unit to another
function convert_unit($value, $from_unit, $to_unit) {
    // Conversion factors
    $conversions = [
        'meter' => [
            'inch' => 39.3700787,
            'foot' => 3.2808399,
            'yard' => 1.0936133,
            'mile' => 0.000621371192
        ],
        'inch' => [
            'meter' => 0.0254,
            'foot' => 0.0833333333,
            'yard' => 0.0277777778,
            'mile' => 0.0000157828283
        ],
        // Add more conversion factors here
    ];

    // Check if the from unit and the to unit are the same
    if ($from_unit == $to_unit) {
        return $value;
    }

    // Check if a conversion factor exists for the from unit and the to unit
    if (!isset($conversions[$from_unit][$to_unit])) {
        // If not, try to find the reverse conversion factor
        if (!isset($conversions[$to_unit][$from_unit])) {
            // If the reverse conversion factor does not exist, return an error message
            return "Error: Conversion from $from_unit to $to_unit is not supported.";
        }
        // If the reverse conversion factor exists, use it to convert the value
        $converted_value = $value / $conversions[$to_unit][$from_unit];
    } else {
        // If a conversion factor exists, use it to convert the value
        $converted_value = $value * $conversions[$from_unit][$to_unit];
    }

    return $converted_value;
}

// Test the function
$value = 10;
$from_unit = 'meter';
$to_unit = 'inch';
$converted_value = convert_unit($value, $from_unit, $to_unit);
echo "$value $from_unit is equal to $converted_value $to_unit.";