Bug #68507 [Com]: SimpleXML objects casted to boolean inconsistently

Edit report at https://bugs.php.net/bug.php?id=68507&edit=1 ID: 68507 Comment by: jdomenechbborges at gmail dot com Reported by: dmitri dot sologoubenko at gmail dot com Summary: SimpleXML objects casted to boolean inconsistently Status: Open Type: Bug Package: SimpleXML related Operating System: Ubuntu PHP Version: 5.5.19 Block user comment: N Private report: N New Comment: The issue seems to be solved slowly in the next releases starting from PHP 5.4 and in PHP 7.0 seems completely solved. Test site --------- http://phptester.net/ Result in 5.6 ------------- $CHILD [a]: <a attrA="valA">xxx</a> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : true - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): true - (((boolean)$CHILD)?'true':'false'): true $CHILD [b]: <b attrB="valB"/> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : false - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): false - (((boolean)$CHILD)?'true':'false'): true $CHILD [c]: <c>oink</c> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : true - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): true - (((boolean)$CHILD)?'true':'false'): true $CHILD [d]: <d/> - if($CHILD) return 'true'; else return 'false'; : false - if(true == $CHILD) return 'true'; else return 'false'; : false - if((boolean)$CHILD) return 'true'; else return 'false'; : false - (($CHILD)?'true':'false'): false - ((true == $CHILD)?'true':'false'): false - (((boolean)$CHILD)?'true':'false'): false $CHILD [e]: <e><f>zzz</f></e> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : false - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): false - (((boolean)$CHILD)?'true':'false'): true Result in 7.0 ------------- $CHILD [a]: <a attrA="valA">xxx</a> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : true - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): true - (((boolean)$CHILD)?'true':'false'): true $CHILD [b]: <b attrB="valB"/> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : true - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): true - (((boolean)$CHILD)?'true':'false'): true $CHILD [c]: <c>oink</c> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : true - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): true - (((boolean)$CHILD)?'true':'false'): true $CHILD [d]: <d/> - if($CHILD) return 'true'; else return 'false'; : false - if(true == $CHILD) return 'true'; else return 'false'; : false - if((boolean)$CHILD) return 'true'; else return 'false'; : false - (($CHILD)?'true':'false'): false - ((true == $CHILD)?'true':'false'): false - (((boolean)$CHILD)?'true':'false'): false $CHILD [e]: <e><f>zzz</f></e> - if($CHILD) return 'true'; else return 'false'; : true - if(true == $CHILD) return 'true'; else return 'false'; : true - if((boolean)$CHILD) return 'true'; else return 'false'; : true - (($CHILD)?'true':'false'): true - ((true == $CHILD)?'true':'false'): true - (((boolean)$CHILD)?'true':'false'): true Previous Comments: ------------------------------------------------------------------------ [2014-12-09 11:10:25] seo at gacek dot vot dot pl Also consider reading: http://stackoverflow.com/questions/27156276/how-does-php-simplexml-get-evaluated-as-an-expression/27157104?noredirect=1#comment43066341_27157104 and https://bugs.php.net/bug.php?id=68540&thanks=4 for more refference about problem. ------------------------------------------------------------------------ [2014-11-26 18:37:26] dmitri dot sologoubenko at gmail dot com Seems like the general rule - here - is, for bare objects as conditional expressions: the SimpleXML object is considered "true" only and only if it: a) has content or children, and also b) has attributes otherwise it is considered "false" (if block not executed). Comparison to true follows different rules, and so does explicit casting to boolean. Only comparison to boolean follows the description in documentation (and that's implicit casting to boolean!). ------------------------------------------------------------------------ [2014-11-26 18:28:34] dmitri dot sologoubenko at gmail dot com Description: ------------ As per PHP documentation (online, see http://php.net/manual/en/control-structures.if.php): > As described in the section about expressions, expression is evaluated to > its Boolean value. If expression evaluates to TRUE, PHP will execute > statement, and if it evaluates to FALSE - it'll ignore it. More > information about what values evaluate to FALSE can be found in the > 'Converting to boolean' section. The "Converting to boolean" section of this explanation states: > Converting to boolean > When converting to boolean, the following values are considered FALSE: > ...omissis... > SimpleXML objects created from empty tags Children elements "b" and "d" ARE empty (no content), therefore I was expecting "false", and "a", "c", "e" ARE NOT empty, so I was expecting "true". As is comes out, that statement in PHP documentation is absolutely NOT true, and the behaviour doesn't even seem consistent: implicit or explicit casts to boolean don't behave the same way (see case of element "c"), and if the bare SimpleXML object is used as "if" conditional expression (both "if" and ternary operator), somehow that conditional expression evaluates differently from a cast to boolean. Test script: --------------- <?php $xmlString = '<'.'?xml version="1.0" encoding="UTF-8"?'.'>' . '<rootEl>' . '<a attrA="valA">xxx</a>' . '<b attrB="valB"/>' . '<c>oink</c>' . '<d/>'. '<e>' . '<f>zzz</f>' . '</e>' . '</rootEl>'; $xml = simplexml_load_string( $xmlString ); foreach ( $xml->children() as $child ) { echo "\$CHILD [" . $child->getName() . "]: " . $child->asXML(); echo "\n"; $insideIf1 = false; if ($child) { $insideIf1 = true; } $insideIf2 = false; if (true == $child) { $insideIf2 = true; } $insideIf3 = false; if ((boolean)$child) { $insideIf3 = true; } echo " - if(\$CHILD) return \"true\"; else return \"false\"; : " . (($insideIf1)?"true":"false")."\n"; echo " - if(true == \$CHILD) return \"true\"; else return \"false\"; : " . (($insideIf2)?"true":"false")."\n"; echo " - if((boolean)\$CHILD) return \"true\"; else return \"false\"; : " . (($insideIf3)?"true":"false")."\n"; echo " - ((\$CHILD)?\"true\":\"false\"): " . (($child)?"true":"false")."\n"; echo " - ((true == \$CHILD)?\"true\":\"false\"): " . ((true == $child)?"true":"false")."\n"; echo " - (((boolean)\$CHILD)?\"true\":\"false\"): " . (((boolean)$child)?"true":"false")."\n"; echo "\n"; } Expected result: ---------------- $CHILD [a]: <a attrA="valA">xxx</a> - if($CHILD) return "true"; else return "false"; : true - if(true == $CHILD) return "true"; else return "false"; : true - if((boolean)$CHILD) return "true"; else return "false"; : true - (($CHILD)?"true":"false"): true - ((true == $CHILD)?"true":"false"): true - (((boolean)$CHILD)?"true":"false"): true $CHILD [b]: <b attrB="valB"/> - if($CHILD) return "true"; else return "false"; : false - if(true == $CHILD) return "true"; else return "false"; : false - if((boolean)$CHILD) return "true"; else return "false"; : false - (($CHILD)?"true":"false"): false - ((true == $CHILD)?"true":"false"): false - (((boolean)$CHILD)?"true":"false"): false $CHILD [c]: <c>oink</c> - if($CHILD) return "true"; else return "false"; : true - if(true == $CHILD) return "true"; else return "false"; : true - if((boolean)$CHILD) return "true"; else return "false"; : true - (($CHILD)?"true":"false"): true - ((true == $CHILD)?"true":"false"): true - (((boolean)$CHILD)?"true":"false"): true $CHILD [d]: <d/> - if($CHILD) return "true"; else return "false"; : false - if(true == $CHILD) return "true"; else return "false"; : false - if((boolean)$CHILD) return "true"; else return "false"; : false - (($CHILD)?"true":"false"): false - ((true == $CHILD)?"true":"false"): false - (((boolean)$CHILD)?"true":"false"): false $CHILD [e]: <e><f>zzz</f></e> - if($CHILD) return "true"; else return "false"; : true - if(true == $CHILD) return "true"; else return "false"; : true - if((boolean)$CHILD) return "true"; else return "false"; : true - (($CHILD)?"true":"false"): true - ((true == $CHILD)?"true":"false"): true - (((boolean)$CHILD)?"true":"false"): true Actual result: -------------- $CHILD [a]: <a attrA="valA">xxx</a> - if($CHILD) return "true"; else return "false"; : true - if(true == $CHILD) return "true"; else return "false"; : true - if((boolean)$CHILD) return "true"; else return "false"; : true - (($CHILD)?"true":"false"): true - ((true == $CHILD)?"true":"false"): true - (((boolean)$CHILD)?"true":"false"): true $CHILD [b]: <b attrB="valB"/> - if($CHILD) return "true"; else return "false"; : true - if(true == $CHILD) return "true"; else return "false"; : false - if((boolean)$CHILD) return "true"; else return "false"; : true - (($CHILD)?"true":"false"): true - ((true == $CHILD)?"true":"false"): false - (((boolean)$CHILD)?"true":"false"): true $CHILD [c]: <c>oink</c> - if($CHILD) return "true"; else return "false"; : false - if(true == $CHILD) return "true"; else return "false"; : true - if((boolean)$CHILD) return "true"; else return "false"; : false - (($CHILD)?"true":"false"): false - ((true == $CHILD)?"true":"false"): true - (((boolean)$CHILD)?"true":"false"): false $CHILD [d]: <d/> - if($CHILD) return "true"; else return "false"; : false - if(true == $CHILD) return "true"; else return "false"; : false - if((boolean)$CHILD) return "true"; else return "false"; : false - (($CHILD)?"true":"false"): false - ((true == $CHILD)?"true":"false"): false - (((boolean)$CHILD)?"true":"false"): false $CHILD [e]: <e><f>zzz</f></e> - if($CHILD) return "true"; else return "false"; : true - if(true == $CHILD) return "true"; else return "false"; : false - if((boolean)$CHILD) return "true"; else return "false"; : true - (($CHILD)?"true":"false"): true - ((true == $CHILD)?"true":"false"): false - (((boolean)$CHILD)?"true":"false"): true ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=68507&edit=1