What does the "?:" operator mean in PHP?

Question

What the operator means ?: in PHP?

Example:

$a = 0;

$b = false;

$c = 3;

echo $a ?: $b ?: $c;

Upshot:

3

What exactly is he doing in the expression above?

Is that a ternary? If not, what do you call this operation?

Answer 1

This is the operator reduced ternary, as stated in these replies:

• Use of ? and : in php
• Reduced ternary in PHP - Error or misinterpreted?

If the condition passes:

$variavel = 10;
$variavel ?: 5; //Irá imprimir 10

If it is 0, false, NULL or an empty string:

$variavel = NULL;
$variavel ?: 5; //Irá imprimir 5

In other words, the passing condition then uses the value of the condition, it would be the same thing as doing this:

$variavel ? $variavel : 5; //Irá imprimir 5

_{Source: http://php.net/manual/en/language.operators.comparison.php#language.operators.comparison.Ternary}

In his example $a is 0 and $b is false, as I said earlier, are values that do not pass in condition, as explained by @Ricardo and so ends up going to the $c which is the ultimate value.

Recommending

It is highly recommended to avoid the "Stacking" of ternary expressions. PHP’s behavior when using more than one ternary operator in the single command is not obvious to the interpreter, as you did in your example:

 echo $a ?: $b ?: $c;

So avoid this.

Answer 2

That’s a ternary operator with the clause aimed at the result true emptiness.

Hence: how $a is phony enters the second suit that checks whether $b is true or false and is phony enters the clause false of the second ternary which has the value of $c.