PHP Constants

1
PHP - Constants

• Case sensitive
• Convention upper case
• naming rules like any label in PHP (same as
  what follows the sign in variables)
• You can define a constant by using the define( )
  function.
• Once a constant is defined, it can never be
  changed or undefined.

2
PHP - Constants

• Constants do not have a dollar sign () before
  them
• Constants may only be defined using the define( )
  function, not by simple assignment
• Constants may be defined and accessed anywhere
  without regard to variable scoping rules
• Constants may not be redefined or undefined once
  they have been set and
• Constants may only evaluate to scalar values.

3
PHP - Constants

• lt?php define("CONSTANT", "Hello world.")
  echo CONSTANT // ? "Hello world."?gt

4
PHP Magic Constants

• There are five magical constants that change
  depending on where they are used.
• For example, the value of __LINE__ depends on the
  line that it's used on in your script
• These special constants are case-insensitive

5
PHP Magic Constants

• __LINE__ ? current line number
• __FILE__ ? full path and file name
• __FUNCTION__ ? function name
• __CLASS__ ? class name
• __METHOD__ ? method name