不同数据类型之间的php逻辑运算符“或”

Question

<?php

 $sample = (False or 436);
 echo $sample;
?>

I tried this code to identify and have and idea about how operator precedence effects to code. But I'm totally confusing with the answers I got.

 <?php

 $sample = (False or 436);
 echo $sample;
?>

gives answer as 1

<?php

 $sample = (True or 436);
 echo $sample;
?>

gives 1 too

 <?php

 $sample = False or 436;
 echo $sample;
?>

gives nothing.

As I could see whatever I put next to the or the answer was 1

PS I tried them on http://sandbox.onlinephpfunctions.com/ this online editor.

I need to know the is the actual concept behind it.

Answer 1

The reason behind this is something called operator precedence. If you remove the brackets, the assignment $sample = false takes precedence before the or 436 function. The result is echo false , which outputs nothing. That is why you in most cases should use || operator instead.

More information: http://php.net/manual/en/language.operators.precedence.php

Answer 2

You may want to have a read at PHP Type Comparison Tables as well as the Booleans documentation . Pay special attention to Fred Koschara's notes in the top comment, which explains that the OR operator has lower precedence than the assignment operator. You may instead be looking to use || instead of OR, as the || operator does the same thing, but with higher precedence.

Answer 3

As all the answers I got I could find all in one answer for what I posted. I think this may be helpful.

 <?php 
  $var1 = TRUE; 
  $var2 = FALSE; 
  $var3 = 123;


  $x = (int)$var2 or $var3;
  echo $x;// $x assigned to $var2 and type cast into int-display 0

  $y = ($var2 or $var3);
  echo $y;//operation inside the () returns true. so it prints 1

  $n = ($var2 or $var2);
  echo $n;//operation inside the () returns false.It concider as NULL. display nothing
  echo (int)$n;//print numerical value for false-0

  $z = $var2;
  echo $z;//returns 0. It is considered as NULL. so display nothing

 ?>

This is the exact answer I really expected. Thanks.