PHP 写程序测试 NULL "" 0 "0" 1 的区别

本文链接：https://blog.youkuaiyun.com/weixinkaifa/article/details/25287307

这篇博客探讨了PHP编程中常见的几个值：NULL、空字符串''、整数0、字符串'0'和整数1之间的区别。通过测试和示例，解释了在条件判断、空值检测和类型比较中它们各自的行为差异。

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null '' 0 '0' 1 empty isset strlen is_null == 结果如下：

array (size=5)
  'null' => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean false
      'strlen' => int 0
      'is_null' => boolean true
      '$v==''' => boolean true
      '$v==0' => boolean true
      '$v==null' => boolean true
      '$v==false' => boolean true
  '''' => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 0
      'is_null' => boolean false
      '$v==''' => boolean true
      '$v==0' => boolean true
      '$v==null' => boolean true
      '$v==false' => boolean true
  0 => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 1
      'is_null' => boolean false
      '$v==''' => boolean true
      '$v==0' => boolean true
      '$v==null' => boolean true
      '$v==false' => boolean true
  ''0'' => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 1
      'is_null' => boolean false
      '$v==''' => boolean false
      '$v==0' => boolean true
      '$v==null' => boolean false
      '$v==false' => boolean true
  1 => 
    array (size=8)
      'empty' => boolean false
      'isset' => boolean true
      'strlen' => int 1
      'is_null' => boolean false
      '$v==''' => boolean false
      '$v==0' => boolean false
      '$v==null' => boolean false
      '$v==false' => boolean false

PHP 写程序测试 NULL "" 0 "0" 1 的区别

<?php 
$arr = array(null,'',"",0,'0',"0",1);
foreach($arr as $k=>$v){
	$res[] = array('empty'=>empty($v),
			'isset'=>isset($v),
			'strlen'=>strlen($v),
			'is_null'=>is_null($v),
			'$v==\'\''=>$v=='',
			'$v==0'=>$v==0,
			'$v==null'=>$v==null,
			'$v==false'=>$v==false,
			'$v==0'=>$v==0);	
}
var_dump($arr);
var_dump($res);
?>

array (size=7)
  0 => null
  1 => string '' (length=0)
  2 => string '' (length=0)
  3 => int 0
  4 => string '0' (length=1)
  5 => string '0' (length=1)
  6 => int 1
array (size=7)
  0 => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean false
      'strlen' => int 0
      'is_null' => boolean true
      '$v==''' => boolean true
      '$v==0' => boolean true
      '$v==null' => boolean true
      '$v==false' => boolean true
  1 => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 0
      'is_null' => boolean false
      '$v==''' => boolean true
      '$v==0' => boolean true
      '$v==null' => boolean true
      '$v==false' => boolean true
  2 => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 0
      'is_null' => boolean false
      '$v==''' => boolean true
      '$v==0' => boolean true
      '$v==null' => boolean true
      '$v==false' => boolean true
  3 => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 1
      'is_null' => boolean false
      '$v==''' => boolean true
      '$v==0' => boolean true
      '$v==null' => boolean true
      '$v==false' => boolean true
  4 => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 1
      'is_null' => boolean false
      '$v==''' => boolean false
      '$v==0' => boolean true
      '$v==null' => boolean false
      '$v==false' => boolean true
  5 => 
    array (size=8)
      'empty' => boolean true
      'isset' => boolean true
      'strlen' => int 1
      'is_null' => boolean false
      '$v==''' => boolean false
      '$v==0' => boolean true
      '$v==null' => boolean false
      '$v==false' => boolean true
  6 => 
    array (size=8)
      'empty' => boolean false
      'isset' => boolean true
      'strlen' => int 1
      'is_null' => boolean false
      '$v==''' => boolean false
      '$v==0' => boolean false
      '$v==null' => boolean false
      '$v==false' => boolean false