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Request #52482 Casting SimpleXMLElement('0') to boolean results in true
Submitted: 2010-07-29 10:50 UTC Modified: 2021-07-11 04:22 UTC
Votes:2
Avg. Score:3.0 ± 2.0
Reproduced:1 of 1 (100.0%)
Same Version:1 (100.0%)
Same OS:1 (100.0%)
From: sjon at react dot com Assigned: cmb (profile)
Status: No Feedback Package: SimpleXML related
PHP Version: Irrelevant OS: Linux
Private report: No CVE-ID: None
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From: sjon at react dot com
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 [2010-07-29 10:50 UTC] sjon at react dot com 
Description:
------------
I understand the bug I am reporting is described in the manual, which is why I am reporting it as a feature request. When casting SimpleXMLElements to boolean, most values comply with the way PHP casts them. There is however one exception: the string '0' is cast to true, which is unexpected. This is especially annoying when using XmlRpc, which uses <boolean>0</boolean> for its values.

Test script:
---------------
<?php

var_dump((bool)new SimpleXMLElement("<w>0</w>"));

Expected result:
----------------
bool(false)

Actual result:
--------------
bool(true)

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 [2010-07-29 11:02 UTC] salathe@php.net 
You are not casting the string "0" to boolean, you're casting the object. As such, 
it follows normal rules for casting objects. The only time a SimpleXMLElement will 
cast to boolean false is with an "empty" element (e.g. "<w/>").

If you want your sample element to cast to false, you will first need to cast to a 
string: (bool) (string) new SimpleXMLElement...
 [2010-07-29 11:12 UTC] sjon at react dot com 
Then why does this work correctly?

var_dump((int)new SimpleXMLElement("<w>2</w>")); (returns int(2))

The reason is SimpleXMLElements do not follow the normal rules, have a look at simplexml.c line 1762:

    if (type == IS_BOOL) {
        node = php_sxe_get_first_node(sxe, NULL TSRMLS_CC);
        prop_hash = sxe_get_prop_hash(readobj, 1 TSRMLS_CC);
        INIT_PZVAL(writeobj);
        ZVAL_BOOL(writeobj, node != NULL || zend_hash_num_elements(prop_hash) > 0);
        zend_hash_destroy(prop_hash);
        efree(prop_hash);
        return SUCCESS;
    }
 [2010-07-29 12:40 UTC] salathe@php.net 
I didn't mean to suggest this wasn't worth considering.  I'm just wondering 
whether this particular suggestion might cause some impact for folks who already 
make use of the current behaviour.
 [2021-07-02 16:52 UTC] cmb@php.net
-Status: Open +Status: Feedback -Assigned To: +Assigned To: cmb
 [2021-07-02 16:52 UTC] cmb@php.net 
Given that SimpleXMLElements behave this way since they have been
introduced, changing their behavior would require an RFC.

Not sure what to do with this ticket.
 [2021-07-11 04:22 UTC] php-bugs at lists dot php dot net 
No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
If this is not the case and you are able to provide the
information that was requested earlier, please do so and
change the status of the bug back to "Re-Opened". Thank you.
 
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