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| The following is a simple template to create a conversion table. It allow for the loading of multiple conversion equations into an array. Obviously, these equations could be loaded from a flat text file or a database.
The equations are stored in an array and are parsed in the final calculation using the eval() function. This allows for complex functions to be stored. The equation in the array is the part before the equals sign. The part after the equals sign is a description of the conversion to take place. The value to be converted is added to the code by replacing the # in the array with the value. We could have stored the complete code in the array ( ie "$value=$value*0.3" ) but I prefer this method as it gives me the flexability to export the array to other languages ( mainly if I am using a text file to store the formulas ).
You can see a working version of the conversion tables here. |
<?php
$convert = array( "#*0.03937=Millimetres to inches",
"#*0.3937=Centimetres to inches",
"#*2.54=Inches to centimetre",
"#*0.3=Feet to metres")
// $value is the amount we want converted
$value = 2;
// $select is the postion in the above array which stores the
// coversion formula, as well as some descriptive text
$select = 2
// seperate out the formula from the description
$options = explode("=",$convert[$select]);
// replace the # with the value
$formula = str_replace("#",$value,$options[0]);
// use the eval() function to process the equation
eval("\$conversion = $formula;");
// $conversion now holds the converted amount
print("$value = $conversion ( {$options[1]} )");
?>
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Conversion tables A-K