Extracting and converting numbers from text strings

[king.oslo]

Hello my friends,

 

I am trying to make a Body Mass Index (BMI) calulator. It works so that users feed the calulator with their weight and height, and their BMI is calculated. Unfortunatly the way that people feed the calculator with their data seems to vary big time.

 

For example, they may wright that their height is:

 

150cm

1.5meters

ca 150cm

150

..and so on.

 

I need to find some functions or ways to get rid of letters, and convert the ones given in centimeters to meters.

 

Which functions or methods can I use?

 

Thanks

 

Marius

[PFMaBiSmAd]

Don't give them a choice on how to enter the numbers. Use a drop-down select menu.

[ldougherty]

I'd personally have a text field for the number and a select box with cm, meter, etc

 

then you use the information received from the form to do your conversions to whatever metric unit you want to use.

[king.oslo]

I thought about that, is there a way to do what I suggested, though? I thought it was more elegant

 

Thanks,

Marius

[Ken2k7]

preg_replace should work. Here's an example -

preg_replace('#[^\d]#', '', $str);

[thebadbad]

But there's no foolproof solution, because you'd have to take every possible input into account. Here's my shot at a function:

 

<?php
function smart_convert_m($str) {
preg_match('~^([\d,.]+)\s*([a-z.]+)$~iD', trim($str), $matches);
$value = (float) str_replace(',', '.', $matches[1]);
switch ($matches[2]) {
	case 'cm':
	case 'cm.':
	case 'centimetres':
	case 'centimeters':
		$m = $value / 100;
		break;
	case 'm':
	case 'm.':
	case 'metres':
	case 'meters':
		$m = $value;
		break;
	default:
		return false;
}
return $m;
}
//test with samples
$samples = array('1,5 metres', '1.5meters', '1.5m', '150cm', '150centimetres', '150 centimeters');
foreach ($samples as $sample) {
echo "$sample => " . smart_convert_m($sample) . '<br />';
}
?>

Output:

 

1,5 metres => 1.5
1.5meters => 1.5
1.5m => 1.5
150cm => 1.5
150centimetres => 1.5
150 centimeters => 1.5

 

Edit: Added support for cm and m with a trailing dot.