Question

I have been programming in PHP for a while but I still dont understand the difference between == and ===. I know that = is assignment. And == is equals to. So what is the purpose of ===?

Answer 1

It compares both value and type equality.

 if("45" === 45) //false
 if(45 === 45) //true
 if(0 === false)//false

It has an analog: !== which compares type and value inequality

 if("45" !== 45) //true
 if(45 !== 45) //false
 if(0 !== false)//true

It’s especially useful for functions like strpos – which can return 0 validly.

 strpos("hello world", "hello") //0 is the position of "hello"

 //now you try and test if "hello" is in the string...

 if(strpos("hello world", "hello")) 
 //evaluates to false, even though hello is in the string

 if(strpos("hello world", "hello") !== false) 
 //correctly evaluates to true: 0 is not value- and type-equal to false

Here’s a good wikipedia table listing other languages that have an analogy to triple-equals.