$prime(N[,N])[.prev|next]
$prime(5) => $true
$prime(4) => $false
$prime(4).next => 5
$prime(4).prev => 3
$prime(6,1) => 5 OR 7
$prime(6,2) => 5,7
$prime(6,2).next => 7,11
$prime(6,2).prev => 5,3

[b]Prime numbers[/b]
As in the style of most of my challenges this is split up into sections which contain tasks of varying difficulty. you may only enter ONE section

[b]Beginners[/b]
[b]Syntax:[/b] $prime(N)
[b]Rules:[/b]
- You may assume that $1 will always be an integer greater than 1, and that input will always be valid
- if N is a prime number you should return $true
- if N is not a prime number you should return either $false or $null
[b]Examples:[/b]
$prime(5) => $true
$prime(9) => $false OR $null 

[b]Intermediate:[/b]
[b]Syntax:[/b] $prime(N)[.prev|.next]
[b]Rules:[/b]
- You may assume that $1 will always be a valid input, however if $2 exists you should return $false (or $null)
- if $1 is a prime number you should return $true - even if a property is specified
- if $1 is not a prime number and no property is specified (or if the property is not prev or next) you should return $false
- if $1 is not a prime number and the property is prev or next you should return the previous, or the next prime number respectively
[b]Examples:[/b]
$prime(5)      => $true
$prime(5).next => $true
$prime(4)      => $false
$prime(4).next => 5
$prime(4).prev => 3
$prime(-4)     => $false
$prime(4,5)    => $false (OR $null)

[b]Advanced:[/b]
[b]Syntax:[/b] $prime(N[,N])[.prev|.next]
[b]Rules:[/b]
- if $1 is a prime number you should return $true - even if a property is specified
- if $1 is not a prime number and no property is specified (or if the property is not prev or next) you should return $false
- if $1 is not a prime number and the property is prev or next you should return the previous, or the next prime number respectively
- if $2 is given and the property is either prev or next you should return the previous or next N prime numbers respectively 
- if $2 is given but no valid property (ie prev or next) is specified you should return the closet N integers sorted by how far they are from $1
- When returning multiple numbers, they should be comma delimited
- you may assume that both $1 and $2 will be valid - however if $2 exists you should return $false (or $null)

[b]Examples:[/b]
[i] ALl examples from the intermediate section apply here as well - apart from the final one, which is redefined here[/i]
$prime(5,2) => $true
$prime(8,2) => 7,5 OR 7,11
$prime(8,3) => 7,5,11
$prime(8,4).next => 11,13,17,19
$prime(8,4).prev => 7,5,3,-1
$prime(-5) => $true
$prime(4,5) => -1,3,5,7 OR -1,5,3,7