defined(3) [php man page]

DEFINED(3)								 1								DEFINED(3)

defined - Checks whether a given named constant exists

SYNOPSIS

       bool defined (string  $name)

DESCRIPTION

	Checks whether the given constant exists and is defined.

       Note

	       If  you	want  to  see if a variable exists, use isset(3) as defined(3) only applies to constants. If you want to see if a function
	      exists, use function_exists(3).

PARAMETERS

	      o $name
		- The constant name.

RETURN VALUES

	Returns TRUE if the named constant given by $name has been defined, FALSE otherwise.

EXAMPLES

       Example #1

	      Checking Constants

	      <?php
	      /* Note the use of quotes, this is important.  This example is checking
	       * if the string 'TEST' is the name of a constant named TEST */
	      if (defined('TEST')) {
		  echo TEST;
	      }
	      ?>

SEE ALSO

       define(3), constant(3), get_defined_constants(3), function_exists(3), The section on Constants.

PHP Documentation Group 														DEFINED(3)

CONSTANT(3)								 1							       CONSTANT(3)

constant - Returns the value of a constant

SYNOPSIS

       mixed constant (string  $name)

DESCRIPTION

	Return the value of the constant indicated by $name.

       constant(3)  is	useful	if  you  need  to  retrieve  the value of a constant, but do not know its name. I.e. it is stored in a variable or
       returned by a function.

	This function works also with class constants.

PARAMETERS

	      o $name
		- The constant name.

RETURN VALUES

	Returns the value of the constant, or NULL if the constant is not defined.

ERRORS
/EXCEPTIONS
	An E_WARNING level error is generated if the constant is not defined.

EXAMPLES

       Example #1

	      constant(3) example

	      <?php

	      define("MAXSIZE", 100);

	      echo MAXSIZE;
	      echo constant("MAXSIZE"); // same thing as the previous line

	      interface bar {
		  const test = 'foobar!';
	      }

	      class foo {
		  const test = 'foobar!';
	      }

	      $const = 'test';

	      var_dump(constant('bar::'. $const)); // string(7) "foobar!"
	      var_dump(constant('foo::'. $const)); // string(7) "foobar!"

	      ?>

SEE ALSO

       define(3), defined(3), The section on Constants.

PHP Documentation Group 													       CONSTANT(3)