Short circuit evaluation and include
| From: | Yeti | Date: | Tue, 02 Dec 2008 10:55:20 +0000 |
| Subject: | Short circuit evaluation and include | ||
| Groups: | php.general | ||
| Request: | Send a blank email to php-general+get-283986@lists.php.net to get a copy of this message | ||
Hello everyone,
I'm posting this as a warning when using include() or include_once()
and checking their return values.
I'm refactoring someone else's code at the moment and got a short
circuit evaluation problem that made some problems ..
Here's the code:
FILE "some_file.php":
<?php
function some_function($file) {
$obj = false;
if (
!isset($file)
|| !is_string($file)
|| !is_readable($file)
|| !include_once($file)
|| !class_exists('some_class')
|| !is_a(($obj = new some_class()), 'some_class')
|| !method_exists($obj, 'some_method')
|| !$obj->some_method()
) return false; // line 14
return $obj;
}
$file = 'some_class.php';
some_function($file);
?>
FILE "some_class.php":
<?php
class some_class {
function some_method() {
return true;
}
}
?>
ERRORS PRODUCED:
Warning: some_function(1) [function.some-function]: failed to open
stream: No such file or directory in */some_file.php on line 14
Warning: some_function() [function.include]: Failed opening '1' for
inclusion (include_path='.;*/php/pear/') in */some_file.php on line 14
Note: I ran this code in PHP 4.4.9
It seemed to me like include_once() was not fully executed or
something when "short circuited", because this code worked just fine
...
FILE "some_file.php":
<?php
function some_function($file) {
$obj = false;
if (
!isset($file)
|| !is_string($file)
|| !is_readable($file)
|| !include_once($file)
) return false;
if (
!class_exists('some_class')
|| !is_a(($obj = new some_class()), 'some_class')
|| !method_exists($obj, 'some_method')
|| !$obj->some_method()
) return false;
return $obj;
}
$file = 'some_class.php';
var_dump(some_function($file));
?>
OUTPUT:
object(some_class)(0) {
}
So I was wondering how include() or include_once() are actually being
executed. I know they both return int(1) if no return specified in the
included file.
That's why I had a glance at the manual [1], where I saw this ..
Because include() is a special language construct, parentheses are not
needed around its argument. Take care when comparing return value.
Example #4 Comparing return value of include
<?php
// won't work, evaluated as include(('vars.php') == 'OK'), i.e.
include('')
if (include('vars.php') == 'OK') {
echo 'OK';
}
// works
if ((include 'vars.php') == 'OK') {
echo 'OK';
}
?>
So when I added the paranthesis it worked ...
FILE "some_file.php":
<?php
function some_function($file) {
$obj = false;
if (
!isset($file)
|| !is_string($file)
|| !is_readable($file)
|| !(include_once($file)) // <--- added paranthesis
|| !class_exists('some_class')
|| !is_a(($obj = new some_class()), 'some_class')
|| !method_exists($obj, 'some_method')
|| !$obj->some_method()
) return false;
return $obj;
}
$file = 'some_class.php';
var_dump(some_function($file));
?>
Me, after an hour of coding without a line of code.
[1] http://in.php.net/manual/en/function.include.php