I was just playing around with PHP, can someone please explain to me why the code below prints out 5566 instead of 6666?
$a = 5; $b = $a; echo $a++ . $b++; echo "\n"; echo $a++ . $b++; Does it echo $a then add 1 to it? Why doesn't it echo the result?
EDIT: Another simple example for anyone viewing:
$a = 5; $b = $a++; echo $a++ . $b; Produces 65
it should be echoing out
55 66 because when you place ++ after (suffix) then the increment is done after the statment is executed. if you want
66 66 then do
$a = 5; $b = $a; echo ++$a . ++$b; echo "\n"; echo $a++ . $b++; It is a POST-INCREMENT OPERATOR so the value is first being used(i.e. 5) and then incremented so you are getting 5566.
echo $a++ . $b++; // echo 55 and then a becomes 6 , b becomes 6 echo "\n"; echo $a++ . $b++; // echo 66 In Your code, IN first echo it returns the $a 's value after that it increment similar to $b.
Here is the $a++ explanation:
++$a Pre-increment Increments $a by one, then returns $a. $a++ Post-increment Returns $a, then increments $a by one. --$a Pre-decrement Decrements $a by one, then returns $a. $a-- Post-decrement Returns $a, then decrements $a by one. Hope this will be helpful to you to understand.
Check below questions also:
Pre-incrementation vs. post-incrementation
What's the difference between ++$i and $i++ in PHP?
Because $a++ is post increment it return value and then increment the value.
try:
echo ++$a . ++$b; echo "\n"; echo $a++ . $b++; it's the same as
$a++; $b++; echo $a . $b; echo "\n"; echo $a . $b; $a++ $b++; When you do postincrementation firstly the value is returned and then it is incremented by 1 that is why you get such results.
If you do preincremenation firstly value to $a is added then it is returned in that cause you will see 66 and 77
echo ++$a . ++$b; will print 66 as you probably expected.
Notice pre incremenation/decrementaiton is faster than post that is why if you don't need to display the value firstly before incremenation/decremation use it.
Morover, if you use reference
$a = 5; $b = &$a; echo $a++ . $b++; It will output 56
and
$a = 5; $b = &$a; echo ++$a . ++$b; will output 77 :)
