Using PHP 5.3 I'm experiencing weird / non-intuitive behavior when applying empty()
to dynamic object properties fetched via the __get()
overload function. Consider the following code snippet:
<?php
class Test {
protected $_data= array(
'id'=> 23,
'name'=> 'my string'
);
function __get($k) {
return $this->_data[$k];
}
}
$test= new Test();
var_dump("Accessing directly:");
var_dump($test->name);
var_dump($test->id);
var_dump(empty($test->name));
var_dump(empty($test->id));
var_dump("Accessing after variable assignment:");
$name= $test->name;
$id= $test->id;
var_dump($name);
var_dump($id);
var_dump(empty($name));
var_dump(empty($id));
?>
The output of this function is as follow. Compare the results of the empty()
checks on the first and second result sets:
Set #1, unexpected result:
string(19) "Accessing directly:"
string(9) "my string"
int(23)
bool(true)
bool(true)
Expecting Set #1 to return the same as Set #2:
开发者_运维百科string(36) "Accessing after variable assignment:"
string(9) "my string"
int(23)
bool(false)
bool(false)
This is really baffling and non-intuitive. The object properties output non-empty strings but empty()
considers them to be empty strings. What's going on here?
Based on a reading of the empty
's manual page and comments (Ctrl-F for isset and/or double underscores), it looks like this is known behavior, and if you want your __set
and __get
methods and empty
to play nice together, there's an implicit assumption that you implement a __isset
magic method as well.
It is a little bit unintuitive and confusing, but that tends to happen with most meta-programming, particularly in a system like PHP.
In this example, empty() calls the __isset() overload function, not the __get() overload function. Try this:
class Test {
protected $_data= array(
'id'=> 23,
'name'=> 'my string'
);
function __get($k) {
return $this->_data[$k];
}
function __isset($k) {
return isset($this->_data[$k]);
}
}
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