# Challenge 1: Replica of PHP's "max" Function

Test your knowledge by writing a replica function of PHP's max function.

## Problem statement

Write a version of PHP’s max function called `_max`

that utilizes the `fold`

operation of the `bingo-functional`

library. Ensure that only non-negative integers are compared and other value types evaluate to `0`

.

The `_max`

function should receive an array as a parameter and return the integer with the maximum value in the case that the array contains all non-negative integers and a `0`

in all other cases.

## Sample inputs and outputs

### Sample input 1

```
$list = [10,12,14,16,18]
```

### Expected output

```
18
```

### Sample input 2

```
$list = [-1,-3,-5]
```

### Expected output

```
0
```

### Sample input 3

```
$list = [a,b,c,d,e]
```

### Expected output

```
0
```

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