PHP goto control structure infinite execution

Question

This seems to execute like an infinite loop.

a:
    echo "Statement 1 \n";
b:
    echo "Statement 2 \n";
if(1 > 2)
    goto a;
else
    goto b;

But this works correctly.

if(1 > 2)
    goto a;
else
    goto b;
a:
    echo "Statement 1 \n";
b:
    echo "Statement 2 \n";

What makes the difference.How can i execute some block of code again like in the first case.Example

$b = 1;
$c = 2;
$a = $b+$c;

if($a > $ b)
  // here i want to cal $a = $b+$c; without using function or copy pasting the code.

You should probably avoid using GOTOs if you can, and if you can't, you may be doing something wrong. Why not just use a function instead? — ElefantPhace, May 20 '14 at 03:43
Why don't you want to use a function? Also a will always be greater than b in this case — ElefantPhace, May 20 '14 at 03:49

score 2 · Answer 1 · answered May 20 '14 at 03:36

2

goto will jump to that part of the code. So in the first case you jump up and start again at b: and then you do that over and over again. But in the second case you jump down.

answered May 20 '14 at 03:36

WizKid

4,888
2
23
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1

It doesn't just execute that first line under your `b:` label. As WizKid says, it **jumps** and continues on with all the code after, thus giving you your infinite loop – ElefantPhace May 20 '14 at 03:40

Sverri M. Olsen · Accepted Answer · 2014-05-20T05:38:09.293

It is an infinite loop because... your code is an infinite loop!

    a:
        echo "...";
.-- b: <------------.
|       echo "..."; |
|   if(1 > 2)       |
|       goto a;     |
|   else            |
`-----> goto b; ----´

It will output:

Statement 1
Statement 2
Statement 2
Statement 2
Statement 2
[...]

Named sections of code (a: and b:) do not stop the script; they are just names that you can jump to. Named sections of code will always be executed if reached.

PHP goto control structure infinite execution

2 Answers2