Web Programming with PHP

Variables

Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive.

PHP supports eight primitive types:

• Four scalar types:
  • boolean
  • integer
  • float (floating-point number, aka double)
  • string
• Two compound types:
  • array
  • object
• And finally three special types:
  • resource
  • NULL
  • callable

// Integers: decimal, octal or hexadecimal
$Var = 123;

// Floating point
$Var = 1.3e4;

// Arrays or vectors
$Var[2] = 123;

// Text Strings
$Var = "A Text String\n";

// Objects
$Var = new oMyClass();

The scope of a variable is the context within which it is defined.

Constants

A constant is an identifier (name) for a simple value. That value cannot change during the execution of the script. A constant is case-sensitive by default. By convention, constant identifiers are always uppercase

There are two built-in constants, TRUE and FALSE (case-insensitive), which representthe two possible boolean values.

Expressions

Expressions are the most important building stones of PHP. The most basic forms of expressions are constants and variables.

A very common type of expressions are comparison expressions. These expressions evaluate to either FALSE or TRUE. These expressions are most commonly used inside conditional execution, such as if statements.

Operators

• Operator Precedence
• Arithmetic Operators
• Assignment Operators
• Bitwise Operators
• Comparison Operators
• Error Control Operators
• Execution Operators
• Incrementing/Decrementing Operators
• Logical Operators
• String Operators
• Array Operators
• Type Operators