```
<?php
function eucDistance(array $a, array $b) {
return
array_sum(
array_map(
function($x, $y) {
return abs($x - $y) ** 2;
}, $a, $b
)
) ** (1/2);
}
// now use it with any array
// make sure both arrays have the same number of elements
echo eucDistance([1,2,5,6,4.6], [4,6,33,45,2.5]);
```

How it works is, we send the two arrays to the `eucDistance()` function as `$a` and `$b`.
The `array_map()` function is used to get an array
of each element which is the square of the difference between two corresponding elements in `$a`
and `$b`. Then, we sum all the values. The square root of the sum is retuned.