String number approximation - php

Question

I was thinking about a "number approximation" function that takes an integer and returns a string, similar to the following:
45 => "some"
100 => "1 hundred"
150 => "over 1 hundred"
1,386 => "over 1 thousand"
15,235,742 => "over 15 million"
797,356,264,255 => "over 700 billion"
I was hoping to use it for, for example, saying how many rows in a database table in an approximate manner.
I couldn't think how to describe such a thing so searching for it has been somewhat tricky.
Does any body know of an existing function (preferably in PHP) that does this, or could anybody describe/point to an algo to get me started on rolling my own?

Answer 1

Take a look at this package: http://pear.php.net/package-info.php?package=Numbers_Words
The following code explained in comments would do it
I've given two options. One only with words. The second that one you have exactly said in your answer. The first one is easier because you don't need to preconvert words to numbers again.
<?php
require_once "Numbers/Words.php";
$number = new Numbers_Words();
$input = "797,356,264,255";
$input = str_replace(',', '',$input); // removing the comas
$output = $input[0]; // take first char (7)
$output2 = $input[0].'00'; //7 + appended 00 = 700 (for displaying 700 instead of 'seven hundred')
for ($i = 1; $i<strlen($input); $i++) {
$output .= '0';
}
$words = $number->toWords($output); //seven hundred billion
$output3 = explode(' ', $words);
$word = $output3[count($output3)-1]; // billion
echo "Over ". $words; // Over seven hundred billion
#####################
echo "Over " . $output2 . ' ' . $word; // Over 700 billion

Answer 2

What do you want to do is so subjective. That's why you cannot find any function to do that.
For your algorithm, you can define some strings which will match with patterns. For example: over ** million matches with a number of 8 digits. You can find the firsts 2 digits and replace ** in the string.
Then you can use math function like round, floor, ceil (it depends of what you want), and find the string corresponding to your pattern.

Answer 3

After a little bit of fiddling I have come up with this:
function numberEstimate($number) {
// Check for some special cases.
if ($number < 1) {
return "zero";
} else if ($number< 1000) {
return "less than 1 thousand";
}
// Define the string suffixes.
$sz = array("thousand", "million", "billion", "trillion", "gazillion");
// Calculate.
$factor = floor((strlen($number) - 1) / 3);
$number = floor(($number / pow(1000, $factor)));
$number = floor(($number / pow(10, strlen($number) - 1))) * pow(10, strlen($number) - 1);
return "over ".$number." ".#$sz[$factor - 1];
}
which outputs something like this:
0 => "zero"
1 => "less than 1 thousand"
10 => "less than 1 thousand"
11 => "less than 1 thousand"
56 => "less than 1 thousand"
99 => "less than 1 thousand"
100 => "less than 1 thousand"
101 => "less than 1 thousand"
465 => "less than 1 thousand"
890 => "less than 1 thousand"
999 => "less than 1 thousand"
1,000 => "over 1 thousand"
1,001 => "over 1 thousand"
1,956 => "over 1 thousand"
56,123 => "over 50 thousand"
99,213 => "over 90 thousand"
168,000 => "over 100 thousand"
796,274 => "over 700 thousand"
999,999 => "over 900 thousand"
1,000,000 => "over 1 million"
1,000,001 => "over 1 million"
5,683,886 => "over 5 million"
56,973,083 => "over 50 million"
964,289,851 => "over 900 million"
769,767,890,753 => "over 700 billion"
7,687,647,652,973,863 => "over 7 gazillion"
It may not be the prettiest solution, or the most elegant, but it seems to work and does a good job so I will probably go along with this.
I thank everyone for the pointers and suggestions!