Booleanos

Este é o tipo mais simples. Um booleano expressa um valor verdade. Ele pode ser TRUE ou FALSE.

Nota: O tipo booleano foi introduzido no PHP 4.

Sintaxe

Para especificar um literal booleano, use as palavras-chave TRUE ou FALSE. Ambas são case-insensitive.

<?php
$foo = True; // atribui o valor True para $foo
?>

Tipicamente você pode utilizar algum tipo de que retorne um valor booleano, e passá-lo para uma .

<?php
// == É um operador que testa
// igualdade e retorna um booleano.
if ($action == "mostrar_versao") {
    echo "A versão é 1.23";
}

// isto não é necessário ...
if ($exibir_separadores == TRUE) {
    echo "<hr>\n";
}

// ... porque você pode simplesmente escrever isso:
if ($exibir_separadores) {
    echo "<hr>\n";
}
?>

Convertendo para booleano

Para converter explicitamente um valor para booleano, utilize-se dos modificadores (bool) ou (boolean). Entretanto, na maioria dos casos, você não precisa utilizar o modificador, desde que qualquer valor será convertido automaticamente se um operador, função ou estrutura de controle requerer um argumento booleano.

Veja também .

Ao converter para booleano, os seguintes valores são considerados FALSE:

Qualquer outro valor é considerado TRUE (incluindo qualquer ).
Aviso

-1 é considerado TRUE, como qualquer valor não zero (negativos ou positivos)!

<?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)
?>

User Contributed Notes

frank at interactinet dot com
Be careful when assigning a value in the if statement, for example:

 if($var = $arg)

$var might be assigned "1" instead of the expected value in $arg.

<?php

public function myMethod()
{
return 'test';
}

public function myOtherMethod()
{
return null;
}

if($val = $this->myMethod())
{
 // $val might be 1 instead of the expected 'test'
}

if( ($val = $this->myMethod()) )
{
// now $val should be 'test'
}

// or to check for false
if( !($val = $this->myMethod()) )
{
// this will not run since $val = 'test' and equates to true
}

// this is an easy way to assign default value only if a value is not returned:

if( !($val = $this->myOtherMethod()) )
{
$val = 'default'
}

?>
oscar at oveas dot com
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;
    }
}
?>
ledadu at gmail dot com
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);

?>
mobil dot boty at no dot spam dot gmail dot com
<?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 ==
fyrye at torntech dot com
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
?>
mercusmaximus at yahoo dot com
Note that the comparison: (false == 0) evaluates to true and so will any value you set to false as well (without casting).
Symbol
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)
russell dot harper at springboardnetworks dot com
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
ashafer01 at gmail dot com
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
admin at eexit dot fr
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
?>
wbcarts at juno dot com
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.
Wackzingo
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.
?>
Steve
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.
Anonymous
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.
artktec at gmail dot com
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
*/
?>
terminatorul at gmail dot com
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.