We are using PHP version 5.5.14


VARIABLES
1 8 2.8 internet
boolean integer double string
bool(true)
int(8)
float(2.8)
string(8) "internet"


QUOTES
With single quotes these are the only escape characters: ', \
With double quotes we have: ", $, 
and variables are evaluated: 8


BOOLEANS
1 1  
true gets echoed as 1
false does not get echoed
1 1
$r1 is false
$r2 is true


NUMBERS
0.5 1 
double integer
0


STRINGS
11

m
matics

0
2
'maths' is not found in 'mathematics'
using == causes us to say the following nonsense...
'math' is not found in 'mathematics'

concatenate
hello world
hello world

array(2) {
  [0]=>
  string(5) "hello"
  [1]=>
  string(5) "world"
}


CONST
3.1415926535898
radius = 8, area = 201.06192982975