issetとis_null

php

メモ

$ar = array();
$ar['aaa'] = "wawawa" ;
$ar['bbb'] = null ;
$ar['ccc'] = "" ;
$ar['ddd'] = 0 ;

foreach($ar as $a ){
	var_dump($a);
	var_dump(isset($a));
	var_dump(is_null($a));
	var_dump("----");
}
var_dump($ar['eee']);
var_dump(isset($ar['eee']));
var_dump(is_null($ar['eee']));
var_dump("----");

#!/usr/local/bin/php
string(6) "wawawa"
bool(true)
bool(false)
string(4) "----"
NULL
bool(false)
bool(true)
string(4) "----"
string(0) ""
bool(true)
bool(false)
string(4) "----"
int(0)
bool(true)
bool(false)
string(4) "----"

Notice: Undefined index:  eee in /xxxxxxx/test.php on line 17

Call Stack:
    0.0004      53000   1. {main}() /xxxxxxx/test.php:0

NULL
bool(false)

Notice: Undefined index:  eee in /xxxxxxx/test.php on line 19

Call Stack:
    0.0004      53000   1. {main}() /xxxxxxx/test.php:0

bool(true)