How to find nearest coordinat in php

[Heeren]

hello
i want to find nearest cordinate of (x,y) in php
like (20,30) i want find the top 5 nearest cordinate to that , how i could this please tell me

[adb64]

Assuming that, next to (x,y), you also have other coordinates (x_n,y_n) then for each pair (x_n,y_n) you can use the following formula:

d_n = (x - x_n)² + (y - y_n)²

When you did that for all coordinate pairs (x_n,y_n), find the five smallest d_n values.
It shouldn't be too complex to translate this into a PHP function.

[Heeren]

thanks for ur formula
but i should do with the database , how should i do with database .
i want to find top 5 nearest abt two cordinate(20,40)
i have two columne X and Y and i want to find nearest 5 record of that cordinate like exp
(19,39),(21,41),(19,41),(20,39)
how should i find throgh query
pls help me

[edited by: Heeren at 6:48 am (utc) on Sep. 21, 2006]

[adb64]

Try something like this:

/* some example values, fill in your own values */ 
$NumberOfCoordinatePairs = 10; 
$x = 20; 
$y = 40; 
for ($i = 0; $i < $NumberOfCoordinatePairs; $i++) 
{ 
 [Some code to get the values from database row $i into $xn[$i] and $yn[$i], find that out yourself] 
 $d[$i] = pow($x - $xn[$i], 2) + pow($y - $yn[$i], 2); 
} 
$a[0] = $a[1] = $a[2] = $a[3] = $a[4] = 9999999999; 
for ($i = 0; $i < $NumberOfCoordinatePairs; $i++) 
{ 
 for ($j = 0 ;$j < 5; $j++) 
 { 
 if ($d[$i] < $a[$j]) 
 { 
 for ($k = 4; $k > $j; $k--) 
 { 
 $a[$k] = $a[$k-1]; 
 } 
 $b[$j] = $i; 
 $a[$j] = $d[$i]; 
 $j = 5; 
 } 
 } 
} 

Now you have an array $b of which each index contains the index into the $xn and $yn arrays of the five coordinates that are nearest to (x,y). When you have less than 5 coordinates to check against not all indexes of $b are set then.
I didn't test this code by the way.
Also it isn't optimised, the two loops can be combined for instance.