翻译自 stackoverflow

==比较的是变量的值是否相等，必要时可进行类型转换；===比较的是变量是否具有相同的值和类型。

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// "===" 意味着两个变量是相同的(值相等，类型相同)  
// "==" 意味着两个变量相等(经过类型转换后，值相等)  
// "!=" 意味着两个变量不相等  

         false   null    array()  0      "0"     0x0     "0x0"   "000"    "0000"  
false    ===     ==      ==       ==      ==     ==      !=      !=       !=    
null     ==      ===     ==       ==      !=     ==      !=      !=       !=    
array()  ==      ==      ===      !=      !=     !=      !=      !=       !=    
0        ==      ==      !=       ===     ==     ===     ==      ==       ==    
"0"      ==      !=      !=       ==      ===    ==      ==      ==       ==    
0x0      ==      ==      !=       ===     ==     ===     ==      ==       ==    
"0x0"    !=      !=      !=       ==      ==     ==      ===     ==       ==    
"000"    !=      !=      !=       ==      ==     ==      ==      ===      ==    
"0000"   !=      !=      !=       ==      ==     ==      ==      ==       ===

注意：

  • "000" == "0000"，这两个变量都可以转换成整数0，即经过类型转换后值相等。
  • false == 0并且false == array()但是array()!=0。