PHP function return false && true && false?

Question

Upgrading from PrestaShop 1.6 to 1.7, I found a change in how the developers return the module install method. Obviously, for both the old and new way, you want to return true if ALL is ok, and false 1.6:

public function install() {
    if(!$this->someFunction() || !parent::install()) 
        return false;
    return true;
}

Sometimes the other way around:

public function install() {
    if($this->someFunction() && parent::install()) 
        return true;
    return false;
}

But now in 1.7 they do it this way, and I cannot figure out how this even works:

public function install() {
    return parent::install()
        && $this->someFunction();
}

How can a function return THIS and THAT? If I was to guess, I would think that it either returns the first TRUE/FALSE and then exits, OR returns the sum of them both (but then only FALSE && FALSE would return FALSE)

Please help me understand this.

return parent::install() && $this->someFunction(); will only return true if parent:install() is true and $this->someFunction() is also true. Else it will return false — Fr0z3n7
– Fr0z3n7, Commented Jun 27, 2018 at 21:37

Richard · Accepted Answer · 2018-06-27 21:39:02Z

2

return this && that is read as return (this && that). this and that will be evaluated to a boolean. If both are true, then it becomes return (true && true). true && true evaluates to true. So, it becomes return true.

It's Boolean Algebra in code form.

answered Jun 27, 2018 at 21:39

Richard

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2 Comments

Pinke Helga Over a year ago

It should be noted that this is particulary valid for PHP. So 1 && 2 evaluates to true in PHP. In some scripting languages, e.g. JavaScript, it works similar, however, the evaluated result is one of the input operands itself. 1 && 2 in JavaScript evaluates to 2 since 1 evaluates to true and the second operand has to be checked as well, thus that second value is returned. 1 || 2 returns 1 in JS and true in PHP.

OnklMaps Over a year ago

A-ha! It was the missing parentheses that made the confusion for me. By adding the parentheses it now makes sense :) And to state the obvious (true && false) will off course evaluate to false.

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