CHECKS if a given named CONSTANT exists.
<?php
bool defined ( str $name )
where,
$name = The constant name to be verified
?>
EXERCISE
<?php
/* - - - - - - - - - - - - - - - - - - - - - - - - - -
USER-DEFINED CONSTANTS
- - - - - - - - - - - - - - - - - - - - - - - - - - */
define('KONST01', 'Haste makes waste. ', FALSE);
// FALSE as default KONST01 ≠ konst01
define('KONST02', 'Haste makes waste. ', TRUE);
// TRUE as default KONST02 = konst02
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool defined ( str $name )
void var_dump ( mix $expression [, mix $... ] )
var_dump ->
RETURN, TRUE or FALSE if applied to USER-DEFINED CONSTANTS
void echo ( str $arg1 [, str $... ] )
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
$vr01U = defined('KONST01');
echo 'KONST01 = ' . KONST01 . '<br>';
var_dump($vr01U);
echo '<br><br>';
echo 'konst01 = ' . konst01 . '<br>';
$vr01L = defined('konst01');
var_dump($vr01L);
echo '<br><br>';
echo 'KONST02 = ' . KONST02 . '<br>';
$vr02U = defined('KONST02');
var_dump($vr02U);
echo '<br><br>';
echo 'konst02 = ' . konst02 . '<br>';
$vr02L = defined('konst02');
var_dump($vr02L);
echo '<br><br>';
?>
EXERCISE
<?php
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool defined ( str $name )
void var_dump ( mix $expression [, mix $... ] )
<<< RETURNS, always, FALSE when applied to
INTERNAL CONSTANTS >>>
var_dump ->
In this case, it RETURNS only, FALSE
void echo ( str $arg1 [, str $... ] )
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
$vl01 = defined(PHP_VERSION);
var_dump($vl01);
echo '<br>( ' . PHP_VERSION . ' )<br><br>';
$vl02 = defined(__LINE__);
var_dump($vl02);
echo '<br><br>';
$vl03 = defined(PHP_INT_MAX);
// AS OF PHP 5.0.5
var_dump($vl03);
echo '<br>( ' . PHP_INT_MAX . ' )<br><br>';
$vl04 = defined(PHP_INT_MIN);
// AS OF PHP 7.0.0
var_dump($vl04);
echo '<br>( ' . PHP_INT_MIN . ' )<br><br>';
$vl05 = defined(TRUE);
var_dump($vl05);
echo '<br><br>';
$vl06 = defined(__DIR__);
var_dump($vl06);
echo '<br><br>';
$vl07 = defined(__FUNCTION__);
var_dump($vl07);
echo '<br><br>';
?>