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(PHP 4, PHP 5)
is_bool — Prüft, ob eine Variable vom Typ boolean ist
Die zu untersuchende Variable.
Gibt TRUE zurück, wenn var vom Typ boolean ist, ansonsten FALSE.
Beispiel #1 is_bool()-Beispiele
<?php
$a = false;
$b = 0;
// Da $a ein Boolean ist, wird true zurückgegeben
if (is_bool($a) === true) {
echo "Ja, das ist ein Boolean";
}
// Da $b kein Boolean ist, wird false zurückgegeben
if (is_bool($b) === false) {
echo "Nein, dies ist kein Boolean";
}
?>
Seems this is a most wanted function, so here is my version of it. I have been using this one for several years no and it works perfect for my needs. I have added "sloppy" human logic to it, and you could easily extend to your flavour. Like in norway some would use "ja" and "nei" instead of "yes" and "no".
<?php
/**
* Checks a variable if it is true or false, humanlike.
* We account for values as 'on', '1', '' and so on.
* Finally, for some reare occurencies we account with
* crazy logic to fit some arrays and objects.
*
* @author Kim Steinhaug, <kim@steinhaug.com>
* @param mixed $var, the variable to check
*
* Example:
* $test = 'true';
* if(_bool($test)){ echo 'true'; } else { echo 'false'; }
*/
function _bool($var){
if(is_bool($var)){
return $var;
} else if($var === NULL || $var === 'NULL' || $var === 'null'){
return false;
} else if(is_string($var)){
$var = trim($var);
if($var=='false'){ return false;
} else if($var=='true'){ return true;
} else if($var=='no'){ return false;
} else if($var=='yes'){ return true;
} else if($var=='off'){ return false;
} else if($var=='on'){ return true;
} else if($var==''){ return false;
} else if(ctype_digit($var)){
if((int) $var)
return true;
else
return false;
} else { return true; }
} else if(ctype_digit((string) $var)){
if((int) $var)
return true;
else
return false;
} else if(is_array($var)){
if(count($var))
return true;
else
return false;
} else if(is_object($var)){
return true;// No reason to (bool) an object, we assume OK for crazy logic
} else {
return true;// Whatever came though must be something, OK for crazy logic
}
}
?>
Here is the function which I use when pasring boolean variables from config files
<?php
function boolVal($var) {
switch ($var) {
case $var == true:
case $var == 1:
// case $var == '1': // no need for this, because we used
// $val == 1 not $var === 1
case strtolower($var) == 'true':
case strtolower($var) == 'on':
case strtolower($var) == 'yes':
case strtolower($var) == 'y':
$out = 1;
break;
default: $out = 0;
}
return $out;
}
?>
I am woundering why php does not have a function to do this
Motaz Abuthiab
Just another little function which doesn't exist yet, but I find mighty useful, especially when working with AJAX and APIs.
<?php
/** Checks a variable to see if it should be considered a boolean true or false.
* Also takes into account some text-based representations of true of false,
* such as 'false','N','yes','on','off', etc.
* @author Samuel Levy <sam+nospam@samuellevy.com>
* @param mixed $in The variable to check
* @param bool $strict If set to false, consider everything that is not false to
* be true.
* @return bool The boolean equivalent or null
*/
function boolval($in, $strict=false) {
$out = null;
// if not strict, we only have to check if something is false
if (in_array($in,array('false', 'False', 'FALSE', 'no', 'No', 'n', 'N', '0', 'off',
'Off', 'OFF', false, 0, null), true)) {
$out = false;
} else if ($strict) {
// if strict, check the equivalent true values
if (in_array($in,array('true', 'True', 'TRUE', 'yes', 'Yes', 'y', 'Y', '1',
'on', 'On', 'ON', true, 1), true)) {
$out = true;
}
} else {
// not strict? let the regular php bool check figure it out (will
// largely default to true)
$out = ($in?true:false);
}
return $out;
}
?>
It may be pretty inefficient, but it does the job.
@ emmanuel del grande
You don't need to break when you return...
function bool($var) {
switch (strtolower($var)) {
case ("true"): return true;
case ("false"): return false;
default: die("whatever you want it to tell");
}
}
@ emanueledelgrande at email dot it
http://us.php.net/manual/en/language.types.type-juggling.php
(bool) or (boolean) is allowed for type casting a variable. No function like intval, etc but the functionality exists.
I think there's a hole in the PHP typecasting methods:
you have the (int) function, the (float) function and the (string) function, but no function to force a string variable into the boolean type.
It's obvious that forcing unconditionally the type of variables into arrays and objects is inappropriate, but boolean type is the most basic one for each programming language, that's why I guessed that a (bool) function already existed.
Moreover, with the increasing trend of RSS data streaming, the parsing of an XML string into an object often requires to typecast as boolean values the content of XML tags, normally returned as string by the object method get_content().
I wrote the following function, which also uses a "native PHP style" error message:
<?php
// strings tyecasting as boolean values:
function bool($var) {
switch (strtolower($var)) {
case ("true"):
return true;
break;
case ("false"):
return false;
break;
default:
die("<br />\n<b>Warning:</b> Invalid argument supplied for ".__FUNCTION__." function in <b>".__FILE__."</b> on line <b>".__LINE__."</b>: the argument can contain only 'true' or 'false' values as a string.<br />\n");
}
}
?>
Here it is a small example:
<?php
$xmlResponse = "<?xml version=\"1.0\" encoding=\"utf-8\"?>";
$xmlResponse .= "<Result>";
$xmlResponse .= "<AuthError>false</AuthError>";
$xmlResponse .= "<TransferStatus>true</TransferStatus>";
$xmlResponse .= "</Result>";
if (! $responseDoc = domxml_open_mem($xmlResponse, DOMXML_LOAD_PARSING, $XmlParsingError)) {
echo "Error while parsing the XML string:<br />".print_r($XmlParsingError, TRUE);
} else {
$ResultNode = $responseDoc->get_elements_by_tagname('Result');
$AuthError = $ResultNode[0]->get_elements_by_tagname('AuthError');
$auth_error = bool($AuthError[0]->get_content());
$TransferStatus = $ResultNode[0]->get_elements_by_tagname('TransferStatus');
$transfer_status = bool($TransferStatus[0]->get_content());
if (! $auth_error) { echo "Auth OK<br />"; } else { echo "Auth error<br />"; }
if ($transfer_status) { echo "Transfer OK<br />"; } else { echo "Transfer error<br />"; }
}
?>
It would be useful this function to be implemented in the core of PHP5.
Small caveat to rh's post: back in PHP 3, "0" would be considered non-empty (i.e., empty would return false), even though (bool) on "0" would also evaluate to false; thus, they would not be complete opposites for someone using PHP 3.
punkpuke is wrong here; what he means to say is that empty($x) is the opposite of (bool)$x. is_bool($x) returns true where $x === false.
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