Store a boolean in an XML document and read using PHP SimpleXML

Question

How do you store booleans in an XML document so that they can be read using the PHP SimpleXML class?

I have the following XML document:

<?xml version='1.0' standalone='yes'?> <status> <investigating></investigating> <log> sample log </log> </status> 

And the following php script to read:

 if (file_exists($filename)) { $statusXml = simplexml_load_file($filename); if ($statusXml) { $investigating = (bool)($statusXml->investigating); echo $investigating; } } else { exit('Failed to open ' . $filename .'.'); } 

No matter what I put in the tag, it is always read as true. I tried "0", an empty string, "false" and a bunch of other ideas, but nothing worked. I thought an empty line should have been due to what I found in this document: http://www.php.net/manual/en/language.types.boolean.php#language.types.boolean.casting

Answer 1

Given that:

• XML data is always a string
• PHP type selection rules can be quite inconsistent.

... I would not rely on automatic juggling. Just determine the syntax that is more convenient for you, drop it into a line when reading and writing your own code for translation into boolean.

 <?php function get_bool($value){ switch( strtolower($value) ){ case 'true': return true; case 'false': return false; default: return NULL; } } $data = '<?xml version="1.0"?> <data> <empty_tag/> <true_tag>true</true_tag> <false_tag>false</false_tag> </data> '; $xml = simplexml_load_string($data); var_dump( get_bool((string)$xml->empty_tag) ); var_dump( get_bool((string)$xml->true_tag) ); var_dump( get_bool((string)$xml->false_tag) ); 

Whatever it is, if you are interested in how to do the work (bool) , you mainly deal with objects, so this rule applies when casting to a logical one:

• SimpleXML objects created from empty tags: FALSE
• Each other value: TRUE

This means that you only get FALSE with <investigating /> (and TRUE with absolutely anything else). The trick I can come up with to expand the range of possible TRUE values ​​is to double cast:

 (bool)(string)$xml->investigating 

Update: Remember to debug var_dump() . If you use echo , you will find that TRUE boolean distinguishes between the string '1' and FALSE to '' (empty string).

Answer 2

You do not capture the right element.

 if (file_exists($filename)) { $statusXml = simplexml_load_file($filename); if ($statusXml = simplexml_load_file($filename)) { $investigating = (bool) $statusXml->investigating[0]; echo $investigating; } } 

Answer 3

It's pretty old, but just in case someone is looking for an answer. You can simply use:

 <example is-true=1> 

or

 <example is-true=0> 

This should work fine.

A note using <example is-true="0"> will return true if you use an if statement on it.