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Dies ist der einfachste Typ. Ein boolean Ausdruck ist ein Wahrheitswert der entweder TRUE (wahr) oder FALSE (falsch) sein kann.
Hinweis: Der boolean Typ wurde in PHP 4 eingeführt.
Ein boolean Wert wird über die Schlüsselworte TRUE und FALSE spezifiziert, Groß- und Kleinschreibung ist dabei nicht von Bedeutung.
<?php
$foo = True; // weist $foo den Wert TRUE zu
?>
Normalerweise wird ein boolean von einem Operator zurückgegeben und an eine Kontrollstruktur weitergegeben.
<?php
// == ist ein Operator der auf Gleichheit prüft
// und ein boolean Ergebnis zurückgibt
if ($action == "show_version") {
echo "Die Version ist 1.23";
}
// die Angabe von '== TRUE' ist hier nicht nötig
if ($show_separators == TRUE) {
echo "<hr>\n";
}
// ... stattdessen funktioniert auch einfach das folgende:
if ($show_separators) {
echo "<hr>\n";
}
?>
To explicitly convert a value to boolean, use the (bool) or (boolean) casts. However, in most cases the cast is unncecessary, since a value will be automatically converted if an operator, function or control structure requires a boolean argument.
Siehe auch Typumwandlungen.
Bei der Konvertierung zum Typ boolean gelten die folgenden Werte als FALSE:
Jeder andere Wert wird als TRUE angenommen (inklusive jeglicher resource Werte).
-1 gilt als TRUE wie jeder andere Integerwert ungleich 0 (egal ob positiv oder negativ)!
<?php
var_dump((bool) ""); // bool(false)
var_dump((bool) 1); // bool(true)
var_dump((bool) -2); // bool(true)
var_dump((bool) "foo"); // bool(true)
var_dump((bool) 2.3e5); // bool(true)
var_dump((bool) array(12)); // bool(true)
var_dump((bool) array()); // bool(false)
var_dump((bool) "false"); // bool(true)
?>
Dunno if someone else posted this solution already, but if not, here's a useful and function to convert strings to strict booleans.
Note this one only checks for string and defaults to the PHP (boolean) cast where e.g. -1 returns true, but you easily add some elseifs for other datatypes.
<?php
function toStrictBoolean ($_val, $_trueValues = array('yes', 'y', 'true'), $_forceLowercase = true)
{
if (is_string($_val)) {
return (in_array(
($_forceLowercase?strtolower($_val):$_val)
, $_trueValues)
);
} else {
return (boolean) $_val;
}
}
?>
Function to sort array by elements and count of element (before php 5.3) (not use Lambda Functions, and Closures)
<?php
//-----------------------------
function arraySortByElements($array2sort,$sortField,$order,$iscount=false) {
$functionString='
if ('.($iscount?'true':'false').'){
if(count($a["'.$sortField.'"]) > count($b["'.$sortField.'"])) return 1*'.$order.';
if(count($a["'.$sortField.'"]) < count($b["'.$sortField.'"])) return -1*'.$order.';
}else{
if($a["'.$sortField.'"] > $b["'.$sortField.'"]) return 1*'.$order.';
if($a["'.$sortField.'"] < $b["'.$sortField.'"]) return -1*'.$order.';
}
return 0;';
usort($array2sort, create_function('$a,$b',$functionString));
return $array2sort;
}
//-----------------------------
//init Array for testing :
$testArray = array(
array('name' => 'Lenny', 'note' => 5, 'listId' => array(654,987,32165)),
array('name' => 'Olivier', 'note' =>3, 'listId' => array(2)),
array('name' => 'Gregory', 'note' => 1, 'listId' => array(45,58)),
array('name' => 'Clement', 'note' => 2, 'listId' => array(584,587,741,14781,147))
);
//sorted Arrays :
$testArrayByNameASC = arraySortByElements($testArray,'name',1);
$testArrayByNoteDESC = arraySortByElements($testArray,'note',-1);
$testArrayByCountlistIdDESC = arraySortByElements($testArray,'listId',-1,true);
?>
<?php
function test() {
return TRUE;
}
$var = test();
// FASE instead of FALSE
if ($var == FASE) {
echo 'function returned FALSE';
} else {
echo 'function returned TRUE';
}
// will output : function returned FALSE
?>
Just spent 10 mins trying to figure out why a function returned false when it didn't, so check your typing or use === instead of ==
Since I haven't seen it posted.
Here is a function that you can use if you have a need to force strict boolean values.
Hopefully this will save someone some time from searching for similar.
<?php
function strictBool($val=false){
return is_integer($val)?false:$val == 1;
}
?>
Simply put, it verifies that the value passed is (bool)true otherwise it's false.
Examples:
__________________________________
<?php
$myBool = strictBool(true);
var_dump($myBool);
//returns (bool)true
$myar = array(0 => true);
$myBool = strictBool($myar[0]);
var_dump($myBool);
//returns (bool)true
$myBool = strictBool("hello");
var_dump($myBool);
//returns (bool)false
$myBool = strictBool(false);
var_dump($myBool);
//returns (bool)false
$myBool = strictBool(array(0 => "hello"));
var_dump($myBool);
//returns (bool)false
$myBool = strictBool(1);
var_dump($myBool);
//returns (bool)false
$myBool = strictBool();
var_dump($myBool);
//returns (bool)false
?>
Note that the comparison: (false == 0) evaluates to true and so will any value you set to false as well (without casting).
Just a side note, doesn't really matters, the reason -1 is true and not false is because boolean type is treated as unsigned, so -1 would be for example, if it's unsigned int32 translate to hex: 0xFFFFFFFF and back to decimal: 4294967295 which is non-zero. there isn't really a "negative boolean". it's a binary thing. :o (since it used to be a bit and then there was only 0 and 1 as an option)
PHP is very fussy converting strings to booleans. The only ones it recognizes are '0' or '', everything else evaluates to TRUE, even 'false' and '0.0' are evaluated as true! I suppose this can't be fixed without breaking a lot of existing code.
Example:
<?php
print 'yes'."\t".((bool)'yes'? 1: 0)."\n";
print 'true'."\t".((bool)'true'? 1: 0)."\n";
print 'no'."\t".((bool)'no'? 1: 0)."\n";
print 'false'."\t".((bool)'false'? 1: 0)."\n";
print '1'."\t".((bool)'1'? 1: 0)."\n";
print '0'."\t".((bool)'0'? 1: 0)."\n";
print '0.0'."\t".((bool)'0.0'? 1: 0)."\n";
print ''."\t".((bool)''? 1: 0)."\n";
?>
Output:
yes 1
true 1
no 1
false 1
1 1
0 0
0.0 1
0
A note when working with PostgreSQL - if you select a boolean field from the database, it returns 't' or 'f'. If you directly evaluate a variable storing a boolean from a PostgreSQL database, it will always return true.
For example...
<?php
$x = pg_query("SELECT someBool FROM atable");
$x = pg_fetch_array($x);
$x = $x['someBool'];
if ($x) echo "true";
else echo "false";
?>
...ALWAYS outputs true
Beware of certain control behavior with boolean and non boolean values :
<?php
// Consider that the 0 could by any parameters including itself
var_dump(0 == 1); // false
var_dump(0 == (bool)'all'); // false
var_dump(0 == 'all'); // TRUE, take care
var_dump(0 === 'all'); // false
// To avoid this behavior, you need to cast your parameter as string like that :
var_dump((string)0 == 'all'); // false
?>
CODING PRACTICE...
Much of the confusion about booleans (but not limited to booleans) is the fact that PHP itself automatically makes a type cast or conversion for you, which may NOT be what you want or expect. In most cases, it's better to provide functions that give your program the exact behavior you want.
<?php
function boolNumber($bValue = false) { // returns integer
return ($bValue ? 1 : 0);
}
function boolString($bValue = false) { // returns string
return ($bValue ? 'true' : 'false');
}
$a = true; // boolean value
echo 'boolean $a AS string = ' . boolString($a) . '<br>'; // boolean as a string
echo 'boolean $a AS number = ' . boolNumber($a) . '<br>'; // boolean as a number
echo '<br>';
$b = (45 > 90); // boolean value
echo 'boolean $b AS string = ' . boolString($b) . '<br>'; // boolean as a string
echo 'boolean $b AS number = ' . boolNumber($b) . '<br>'; // boolean as a number
echo '<br>';
$c = boolNumber(10 > 8) + boolNumber(!(5 > 10)); // adding booleans
echo 'integer $c = ' . $c .'<br>';
?>
Results in the following being printed...
boolean $a AS string = true
boolean $a AS number = 1
boolean $b AS string = false
boolean $b AS number = 0
integer $c = 2
In other words, if we know what we want out of our program, we can create functions to accommodate. Here, we just wanted 'manual control' over numbers and strings, so that PHP doesn't confuse us.
It is correct that TRUE or FALSE should not be used as constants for the numbers 0 and 1. But there may be times when it might be helpful to see the value of the Boolean as a 1 or 0. Here's how to do it.
<?php
$var1 = TRUE;
$var2 = FALSE;
echo $var1; // Will display the number 1
echo $var2; //Will display nothing
/* To get it to display the number 0 for
a false value you have to typecast it: */
echo (int)$var2; //This will display the number 0 for false.
?>
PHP does not break any rules with the values of true and false. The value false is not a constant for the number 0, it is a boolean value that indicates false. The value true is also not a constant for 1, it is a special boolean value that indicates true. It just happens to cast to integer 1 when you print it or use it in an expression, but it's not the same as a constant for the integer value 1 and you shouldn't use it as one. Notice what it says at the top of the page:
A boolean expresses a truth value.
It does not say "a boolean expresses a 0 or 1".
It's true that symbolic constants are specifically designed to always and only reference their constant value. But booleans are not symbolic constants, they are values. If you're trying to add 2 boolean values you might have other problems in your application.
Note that the symbolic constants TRUE and FALSE are treated differently. I was told that this is a feature, not a bug.
echo false ;
echo (false) ;
echo false+false ;
echo (false+false) ;
echo intval(false) ;
echo '"'.false.'"' ;
echo true ;
echo (true) ;
echo true+true ;
echo (true+true) ;
echo intval(true) ;
echo '"'.true.'"' ;
should produce
00000"0"11221"1"
but instead produces
000""11221"1"
In other words, the only way to output the underlying zero or use it in a string is to use 'false+false' or pass it through intval(). No such tricks are required to get at the 1 that underlies true.
The whole idea of symbolic constants is that the underlying value *always* replaces them during translation, and thus anywhere you would otherwise have to use some obscure "magic number" such as 191, you can use a symbolic constant that makes sense, such as TOTAL_NATIONS.
Exactly what php gets out of breaking this rule was not explained to me.
Note you can also use the '!' to convert a number to a boolean, as if it was an explicit (bool) cast then NOT.
So you can do something like:
<?php
$t = !0; // This will === true;
$f = !1; // This will === false;
?>
And non-integers are casted as if to bool, then NOT.
Example:
<?php
$a = !array(); // This will === true;
$a = !array('a'); // This will === false;
$s = !""; // This will === true;
$s = !"hello"; // This will === false;
?>
To cast as if using a (bool) you can NOT the NOT with "!!" (double '!'), then you are casting to the correct (bool).
Example:
<?php
$a = !!array(); // This will === false; (as expected)
/*
This can be a substitute for count($array) > 0 or !(empty($array)) to check to see if an array is empty or not (you would use: !!$array).
*/
$status = (!!$array ? 'complete' : 'incomplete');
$s = !!"testing"; // This will === true; (as expected)
/*
Note: normal casting rules apply so a !!"0" would evaluate to an === false
*/
?>
Beware that "0.00" converts to boolean TRUE !
You may get such a string from your database, if you have columns of type DECIMAL or CURRENCY. In such cases you have to explicitly check if the value is != 0 or to explicitly convert the value to int also, not only to boolean.
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