Question

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Logical Operators, || or OR?

I’ve always thought that OR is another way of writing the || operator in PHP. The only way I prefer using OR over || is that it makes the code easier to read since || can be confused with II or 11 or whatever…

One day I stumbled upon this thing though:

<?php 
      $a = 'string_b';
      $active = ($a == 'string_a') OR
                ($a == 'string_b') OR
                ($a == 'string_c');  
   var_dump($active); // Prints FALSE;
?>

Why is this happening?

Answer 1

The only difference is operator priority, see Operator precedence. || has a higher priority than OR.

By the way, var_dump($a) returns null but prints the right thing, string_b.
But, var_dump($active) will indeed produce an unexpected result, false.
In fact, = has higher priority than or, so your code is equivalent to:

($active = ($a == 'string_a')) OR ($a == 'string_b') OR ($a == 'string_c');

It first assigns false to active, then execute the right part of the first OR.