grid_stuff.php

<?php 


$x = range(40,45,0.25);
$y = range(20,29,0.25);

// var_dump($x);
$v = 43.1;
$v2 = 21.4;
function get4GridPoints($xrange,$yrange,$x,$y,$eps = 0.25){
	$count = 0;
	$xvals = [];
	foreach ($xrange as $value) {
		if($count == 2) break;
		if(abs( $x - $value ) <= $eps){
			$xvals[] = $value;
			$count ++;
		}
	}

	$count = 0;
	$yvals = [];
	foreach ($yrange as $value) {
		if($count == 2) break;
		if(abs( $y - $value ) <= $eps){
			$yvals[] = $value;
			$count ++;
		}
	}

	$res = [];
	foreach ($xvals as $xv) {
		foreach ($yvals as $yv) {
			$res[] = [$xv,$yv];
		}
	}
	return $res;
}

function get4GridIndices($xrange,$yrange,$x,$y,$eps = 0.25){
	$count = 0;
	$xvals = [];
	foreach ($xrange as $key => $value) {
		if($count == 2) break;
		if(abs( $x - $value ) <= $eps){
			$xvals[] = $key;
			$count ++;
		}
	}

	$count = 0;
	$yvals = [];
	foreach ($yrange as $key => $value) {
		if($count == 2) break;
		if(abs( $y - $value ) <= $eps){
			$yvals[] = $key;
			$count ++;
		}
	}

	$res = [];
	foreach ($xvals as $xv) {
		foreach ($yvals as $yv) {
			$res[] = [$xv + $yv*count($yrange)];
		}
	}
	return $res;
}

var_dump(get4GridPoints($x,$y,$v,$v2));
var_dump(get4GridIndices($x,$y,$v,$v2));
?>