Generally a PHP variable has no need to be declared, as happens in other programming languages (like pascal).
A simple variable is like a box: the name of the variable, for example $var, is its identifying label.
The PHP assignment instruction puts a value inside the box:
|$var = 8;||$var is the label, the number 8 is the box content|
The = symbol doesn't mean equality, but assignment!
A simple variable can hold only one value at a time: each new assignment deletes the previous one.
The variable types depend on their content. The simple variable types can be:
|$a = 13;||assignment of a numerical value to $a|
|$a = "giovanni";||assignment of a string to $a|
|$a = TRUE;||assignment of the TRUE boolean constant to $a|
|$a = $a + 1;||increase of 1 the numerical value of $a|
|$a++;||equivalent instruction of $a = $a + 1;|
|$a = $a + $c;||assigns the sum of the numerical values $b and $c to $a|