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phptruthiness

Can't understand validation logic: === vs ==

I'm learning validation stuff, and I just can't understand this:

if (strpos($value, "@") === false) { echo "Validation failed." }

What's the difference between === and ==? and why can't we use == instead and also why is it === false? does false means that @ is not in the $value or it means 0 ?

Solution

  • The Equality Operator ==
    A == B checks whether A and B are equal to each other, but not whether they are the same data type.

    A pertinent example: 0 == false is true

    The Identity Operator ===
    A === B checks whether A and B are equal to each other also the same data type.

    A pertinent example: 0 === false is false

    Application Here

    Applying this to your case, if the @ was found as the first character of the string, strpos($value,"@") would return 0. If it is not found at all, it would return false.

    So to avoid confusing these two situations, the test must use === rather than ==.

    Useful references:

    http://php.net/manual/en/function.strpos.php http://php.net/manual/en/language.operators.comparison.php

    I've assumed this is php, but the equality and identity operators are common to many programming languages.