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HOME>WEBプログラム覚書>PHP empty() isset() is_null() if()
PHP empty() isset() is_null() if()
PHPのempty() isset() is_null() if文の評価について
変数サンプル
PHP
- <?php
- $a = NULL;
- $b = "";
- $c = 0;
- $d = "0";
- $e = 1;
- $f = "1";
- $g = array();
- $h = true;
- $i = false;
- class j {};
- $j = new j();
- $k;
- $l = "null";
- class m {var $a;};
- $m = new m();
- ?>
テストコード
PHP
- <?php
- echo "<h5>is_null()</h5>";
- echo (is_null($a) ? "NULL => true" : "NULL => false") . "<br />";
- echo (is_null($b) ? "'' => true" : "'' => false") . "<br />";
- echo (is_null($c) ? "0 => true" : "0 => false") . "<br />";
- echo (is_null($d) ? "'0' => true" : "'0' => false") . "<br />";
- echo (is_null($e) ? "1 => true" : "1 => false") . "<br />";
- echo (is_null($f) ? "'1' => true" : "'1' => false") . "<br />";
- echo (is_null($g) ? "array() => true" : "array() => false") . "<br />";
- echo (is_null($h) ? "true => true" : "true => false") . "<br />";
- echo (is_null($i) ? "false => true" : "false => false") . "<br />";
- echo (is_null($j) ? "object => true" : "object => false") . "<br />";
- echo (is_null($k) ? "var => true" : "var => false") . "<br />";
- echo (is_null($l) ? "Str null=> true" : "var => false") . "<br />";
- echo "<hr />";
- echo "<h5>empty()</h5>";
- echo (empty($a) ? "NULL => true" : "NULL => false") . "<br />";
- echo (empty($b) ? "'' => true" : "'' => false") . "<br />";
- echo (empty($c) ? "0 => true" : "0 => false") . "<br />";
- echo (empty($d) ? "'0' => true" : "'0' => false") . "<br />";
- echo (empty($e) ? "1 => true" : "1 => false") . "<br />";
- echo (empty($f) ? "'1' => true" : "'1' => false") . "<br />";
- echo (empty($g) ? "array() => true" : "array() => false") . "<br />";
- echo (empty($h) ? "true => true" : "true => false") . "<br />";
- echo (empty($i) ? "false => true" : "false => false") . "<br />";
- echo (empty($j) ? "object => true" : "object => false") . "<br />";
- echo (empty($k) ? "var => true" : "var => false") . "<br />";
- echo (empty($l) ? "Str null=> true" : "var => false") . "<br />";
- echo (empty($m) ? "object2 => true" : "var => false") . "<br />";
- echo "<hr />";
- echo "<h5>isset()</h5>";
- echo (isset($a) ? "NULL => true" : "NULL => false") . "<br />";
- echo (isset($b) ? "'' => true" : "'' => false") . "<br />";
- echo (isset($c) ? "0 => true" : "0 => false") . "<br />";
- echo (isset($d) ? "'0' => true" : "'0' => false") . "<br />";
- echo (isset($e) ? "1 => true" : "1 => false") . "<br />";
- echo (isset($f) ? "'1' => true" : "'1' => false") . "<br />";
- echo (isset($g) ? "array() => true" : "array() => false") . "<br />";
- echo (isset($h) ? "true => true" : "true => false") . "<br />";
- echo (isset($i) ? "false => true" : "false => false") . "<br />";
- echo (isset($j) ? "object => true" : "object => false") . "<br />";
- echo (isset($k) ? "var => true" : "var => false") . "<br />";
- echo (isset($l) ? "Str null=> true" : "var => false") . "<br />";
- ?>
実行結果
is_null()
NULL => true'' => false
0 => false
'0' => false
1 => false
'1' => false
array() => false
true => false
false => false
object => false
Notice: Undefined variable: k in /home/users/1/lolipop.jp-dp07173486/web/_/themes/default/views/pg/2009/03/php_empty_isset_is_null_if.php on line 166
var => true
Str null=> false
empty()
NULL => true'' => true
0 => true
'0' => true
1 => false
'1' => false
array() => true
true => false
false => true
object => false
var => true
Str null=> false
object2 => false
isset()
NULL => false'' => true
0 => true
'0' => true
1 => true
'1' => true
array() => true
true => true
false => true
object => true
var => false
Str null=> true
emptyはPHP4と5で動作が変わってるので注意。
null と 空文字、値がない場合falseにしたいとき。
サンプルコード
PHP
- <?php
- function notNull($key, $var = null) {
- if (!is_null($var) && $var !== '') {
- echo "$key => true" . "<br />";
- } else {
- echo "$key => false" . "<br />";
- }
- }
- echo "<h5>notNull()</h5>";
- notNull("NULL", $a);
- notNull("''", $b);
- notNull("0", $c);
- notNull("'0'", $d);
- notNull("1", $e);
- notNull("'1'", $f);
- notNull("array()", $g);
- notNull("true", $h);
- notNull("false", $i);
- notNull("object", $j);
- notNull("var", $k);
- notNull("Str null", $l);
- notNull("no Arg");
- ?>
実行結果
notNull()
NULL => false'' => false
0 => true
'0' => true
1 => true
'1' => true
array() => true
true => true
false => true
object => true
Notice: Undefined variable: k in /home/users/1/lolipop.jp-dp07173486/web/_/themes/default/views/pg/2009/03/php_empty_isset_is_null_if.php on line 257
var => false
Str null => true
no Arg => false
if文の評価も見ておく
サンプルコード
PHP
- <?php
- echo "<h5>funcIf()</h5>";
- function funcIf($key, $var = null) {
- if ($var) {
- echo "$key => true" . "<br />";
- } else {
- echo "$key => false" . "<br />";
- }
- }
- funcIf("NULL", $a);
- funcIf("''", $b);
- funcIf("0", $c);
- funcIf("'0'", $d);
- funcIf("1", $e);
- funcIf("'1'", $f);
- funcIf("array()", $g);
- funcIf("true", $h);
- funcIf("false", $i);
- funcIf("object", $j);
- funcIf("var", $k);
- funcIf("Str null", $l);
- funcIf("no Arg");
- ?>
実行結果
funcIf()
NULL => false'' => false
0 => false
'0' => false
1 => true
'1' => true
array() => false
true => true
false => false
object => true
Notice: Undefined variable: k in /home/users/1/lolipop.jp-dp07173486/web/_/themes/default/views/pg/2009/03/php_empty_isset_is_null_if.php on line 314
var => false
Str null => true
no Arg => false
| 投稿日 | 2009年3月 5日 13:23 |
|---|---|
| カテゴリ | PHP |
| タグ | テストコード | 関数 |
| トラックバック URL | http://www.kantenna.com/cgi-bin/mt504/mt-tb.cgi/1167 |
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