If-Else 循环 output

Question

<?php
$x = 1;
if ($x == 2)
    print "hi" ;
else if($x = 2)
    print $x;
else
    print "how are u";
?>

Apologies for this basic question as I am a beginner at php.

I was expecting the else statement to be executed and print "how are u", but it executed the elseif statement and printed '2' instead. May I ask why does $x become assigned to 2? Thanks in advance.

Answer 1

You are SETTING x=2 in your else if --> else if($x = 2) -- This would be more appropriate.. Check for absolute === .. Then check for truthy == .. IE

<?php
$x = 1;
if ($x === 2)
    print "hi" ;
else if($x == 2)
    print $x;
else
    print "how are u";
?>

Conversely.. You can play with truthy vs absolute by comparing an integer to string too.. Like:

<?php
$x = 2;
if ($x === 2)                      // Will return true
    print "Is absolute integer" ;
else if($x == 2)                   // Will return true
    print "Is truthy integer";
else if($x === '2')                // Will return false
    print "Is absolute string";
else if($x == '2')                 // Will return true
    print "Is truthy string";
else
    print "how are u";
?>

Which will never reach the else.. But you can see how operators can make or break a program..

Answer 2

<?php $x = 1; if ($x == 2) print "hi" ; else if($x = 2) /* you assign $x 2 and it's true */ print $x; else print "how are u"; ?>

Answer 3

In the elseif you are asigning the number 2 to $x which will always return true. Because of that it will never go to the else block. Dont use = when doing comparisons but == or ===.

   <?php
   $x = 1;
   if ($x == 2)
       print "hi" ;
   else if($x == 2)
       print $x;
   else
       print "how are u";
   ?>

this is the right way to do it. Also it doesnt make sense to check both in if and elseif that $x == 2 since it will never execute the elseif block. Let me try to explain it better, if you do:

if ($x = 2)

thats will assign 2 to $x and this is then the same as:

if ($x)

since the $x now holds the number 2 this is also the same as:

if (2)

this is always true so it will never go to further checks no matter what the number is.

Answer 4

This is because = is assignment operator not comparison like == . That is why $x is assigned value 2 and the else if condition is met and executed.