why php cannot show variable in string template under some circumstances?

Question

Thanks for your time in advance. I am a newbie in php and encountered a strange problem, at least for me it is strange. It is about showing variable in string template. Please see the code below:

public function welcome() {
    $data="everyone";
    $b = $this->returnTemplate();
    $a = "<div>dear $data</div>";
}
public function returnTemplate()
{
    return "<div>dear $data</div>";
}

I just thought both $a and $b should be the same value <div>dear everyone</div> but in fact only $a is while $b is <div>dear </div>. That really puzzled me and I wonder why? Could someone please to explain it to me?

Thanks in advance and any feedback is welcome!

It's called [variable scope](http://www.php.net/manual/en/language.variables.scope.php), and it's fully documented — Mark Baker, Aug 19 '15 at 15:05

score 1 · Accepted Answer · answered Aug 19 '15 at 15:07

1

You are encountering 'variable scope'. As you have defined the variable $data in the welcome() function, it will not be available anywhere outside of that function. To overcome this, either move it out of the function OR pass it as a parameter to the returnTemplate function.

More info: http://php.net/manual/en/language.variables.scope.php

answered Aug 19 '15 at 15:07

mfisher91

805
1
8
23

many thanks, that seems a stupid question, I know how to do now – Rang-ji Hu Aug 19 '15 at 23:56

score 0 · Answer 2 · answered Aug 19 '15 at 15:06

0

public function welcome() {
 $data="everyone";
 $b = $this->returnTemplate($data);
 $a = "<div>dear $data</div>";
}
public function returnTemplate($data)
{
  return "<div>dear $data</div>";
}

this works.

http://php.net/manual/en/language.variables.scope.php

answered Aug 19 '15 at 15:06

messerbill

5,499
1
27
38

great, I know the reason now, thanks for your time – Rang-ji Hu Aug 19 '15 at 23:57

score 0 · Answer 3 · answered Aug 19 '15 at 15:20

Like already mentioned, you are trying to breach the variable scope. In other words you are trying to use a local variable out of its scope (the function you have initially declared/defined in). There are two ways to achieve what you are trying:

1) Pass the variable as a parameter to the function and then use the returned value, something like this:

public function welcome() {
 $data="everyone";
 $b = $this->returnTemplate($data);
 $a = "<div>dear $data</div>";
}
public function returnTemplate($data)
{
  return "<div>dear $data</div>";
}

2) Declare the variable as GLOBAL on the top/start. So it will have a scope out of that particular function and achieve exactly what you are trying to.

thanks a lot, I know how to do now~ – Rang-ji Hu Aug 19 '15 at 23:55 — Rang-ji Hu, Aug 19 '15 at 23:55

why php cannot show variable in string template under some circumstances?

3 Answers3