如何使用php equalto运算符（关系运算符）[重复]

I have a big confusion over equal to operators(==.===), below I mentioned php code where checking condition that string "all" equal to numeric 0. But it returns true at double equal to ("all"==0), but not with others:

<?php    
    var_dump("all"==0);
    var_dump("all"=="0");
    var_dump("all"==="0");
    var_dump("all"===0);    
?>

Output:

bool(true) 
bool(false)
bool(false) 
bool(false) 

for all the condition the answer should be false. but why "all"==0 is true. can anyone explain?

</div>

=== is Identical operator which performs a 'typesafe comparison'.

That means that it will only return true if both operands have the same type and the same value.