Tabela de comparações de tipos do PHP

As seguintes tabelas demonstram o comportamento dos tipos e operadores de comparação no PHP, tanto para comparações aproximadas ou exatas. Este complemento é também relacionado com a seção do manual sobre type juggling. A inspiração vem dos comentários de vários usuários e do trabalho feito pela » BlueShoes.

Antes de utilizar essas tabelas, é importante entender os tipos e seus significados. Por exemplo, "42" é uma string enquanto 42 é um int. false é um bool enquanto "false" é uma string.

Nota:

Formulários HTML não passam inteiros, floats ou booleanos; eles passam strings. Para saber se uma string é do tipo númerico, você pode usar a função is_numeric().

Nota:

Usar apenas if ($x) quando $x estiver indefinido irá gerar um erro do nível E_NOTICE. Em vez disso, considere usar empty() ou isset() ou ainda inicialize suas variáveis.

Nota:

Algumas operações númericas podem resultar em um valor representado pela constante NAN. Quaisquer comparações exatas ou aproximadas deste valor contra qualquer outro valor, incluindo ele mesmo, com exceção de true, terão como resultado false. (por exemplo NAN != NAN e NAN !== NAN) Exemplos de operações que geram NAN são sqrt(-1), asin(2), e acosh(0).

Comparações de $x com funções PHP
Expression gettype() empty() is_null() isset() bool : if($x)
$x = ""; string true false true false
$x = null; NULL true true false false
var $x; NULL true true false false
$x is undefined NULL true true false false
$x = []; array true false true false
$x = ['a', 'b']; array false false true true
$x = false; bool true false true false
$x = true; bool false false true true
$x = 1; int false false true true
$x = 42; int false false true true
$x = 0; int true false true false
$x = -1; int false false true true
$x = "1"; string false false true true
$x = "0"; string true false true false
$x = "-1"; string false false true true
$x = "php"; string false false true true
$x = "true"; string false false true true
$x = "false"; string false false true true

Comparações aproximadas com ==
true false 1 0 -1 "1" "0" "-1" null [] "php" ""
true true false true false true true false true false false true false
false false true false true false false true false true true false true
1 true false true false false true false false false false false false
0 false true false true false false true false true false false* false*
-1 true false false false true false false true false false false false
"1" true false true false false true false false false false false false
"0" false true false true false false true false false false false false
"-1" true false false false true false false true false false false false
null false true false true false false false false true true false true
[] false true false false false false false false true true false false
"php" true false false false* false false false false false false true false
"" false true false false* false false false false true false false true
* true anteriormente ao PHP 8.0.0.

Comparações exatas com ===
true false 1 0 -1 "1" "0" "-1" null [] "php" ""
true true false false false false false false false false false false false
false false true false false false false false false false false false false
1 false false true false false false false false false false false false
0 false false false true false false false false false false false false
-1 false false false false true false false false false false false false
"1" false false false false false true false false false false false false
"0" false false false false false false true false false false false false
"-1" false false false false false false false true false false false false
null false false false false false false false false true false false false
[] false false false false false false false false false true false false
"php" false false false false false false false false false false true false
"" false false false false false false false false false false false true

adicione uma nota

Notas Enviadas por Usuários (em inglês) 8 notes

up
55
php at benizi dot com
14 years ago
It's interesting to note that 'empty()' and 'boolean : if($x)'
are paired as logical opposites, as are 'is_null()' and 'isset()'.
up
25
Jan
18 years ago
Note that php comparison is not transitive:

"php" == 0 => true
0 == null => true
null == "php" => false
up
24
frank
17 years ago
A comparison table for <=,<,=>,> would be nice...
Following are TRUE (tested PHP4&5):
NULL <= -1
NULL <= 0
NULL <= 1
!(NULL >= -1)
NULL >= 0
!(NULL >= 1)
That was a surprise for me (and it is not like SQL, I would like to have the option to have SQL semantics with NULL...).
up
2
Jeroen
1 year ago
Be aware of the difference between checking the *value* of an array item, and checking the *existence* of an array item:
<?php
$arr
= [
'x' => 0,
'y' => null,
];

isset(
$arr['x']); // true, same as isset(0)
isset($arr['y']); // false, same as isset(null)

array_key_exists('y', $arr); // true, though the value is null
array_key_exists('z', $arr); // false
up
10
edgar at goodforall dot eu
14 years ago
Some function to write out your own comparisson table in tsv format. Can be easily modified to add more testcases and/or binary functions. It will test all comparables against each other with all functions.

<?php
$funcs
= array(
/* Testing equality */
'eq' => '==',
'ne' => '!=',
'gt' => '>',
'lt' => '<',
'ne2' => '<>',
'lte' => '<=',
'gte' => '>=',
/* Testing identity */
'id' => '===',
'nid' => '!=='
);
class
Test {
protected
$a;
public
$b;
public function
__construct($a,$b){
$this->a = $a;
$this->b = $b;
}
public function
getab(){
return
$this->a.",". $this->b;
}

}
$tst1 = new Test(1,2);
$tst2 = new Test(1,2);
$tst3 = new Test(2,2);
$tst4 = new Test(1,1);

$arr1 = array(1,2,3);
$arr2 = array(2,3,4);
$arr3 = array('a','b','c','d');
$arr4 = array('a','b','c');
$arr5 = array();

$comp1 = array(
'ints' => array(-1,0,1,2),
'floats' => array(-1.1,0.0,1.1,2.0),
'string' => array('str', 'str1', '', '1'),
'bools' => array(true, false),
'null' => array(null),
'objects' => array($tst1,$tst2,$tst3,$tst4),
'arrays' => array($arr1, $arr2, $arr3, $arr4, $arr5)
);
$fbody = array();

foreach(
$funcs as $name => $op){
$fbody[$name] = create_function('$a,$b', 'return $a ' . $op . ' $b;');
}

$table = array(array('function', 'comp1', 'comp2', 'f comp1 comp2', 'type'));
/* Do comparisons */
$comp2 = array();
foreach(
$comp1 as $type => $val){
$comp2[$type] = $val;
}

foreach(
$comp1 as $key1 => $val1){
foreach(
$comp2 as $key2 => $val2){
addTableEntry($key1, $key2, $val1, $val2);
}
}
$out = '';
foreach(
$table as $row){
$out .= sprintf("%-20s\t%-20s\t%-20s\t%-20s\t%-20s\n", $row[0], $row[1], $row[2], $row[3], $row[4]);
}

print
$out;
exit;

function
addTableEntry($n1, $n2, $comp1, $comp2){
global
$table, $fbody;
foreach(
$fbody as $fname => $func){
foreach(
$comp1 as $val1){
foreach(
$comp2 as $val2){
$val = $func($val1,$val2);
$table[] = array($fname, gettype($val1) . ' => ' . sprintval($val1), gettype($val2) .' => ' . sprintval($val2), gettype($val) . ' => ' . sprintval($val), gettype($val1) . "-" . gettype($val2) . '-' . $fname);
}
}
}
}

function
sprintval($val){
if(
is_object($val)){
return
'object-' . $val->getab();
}
if(
is_array($val)){
return
implode(',', $val);
}
if(
is_bool($val)){
if(
$val){
return
'true';
}
return
'false';
}
return
strval($val);
}

?>
up
7
blue dot hirano at gmail dot com
10 years ago
The truth tables really ought to be colorized; they're very hard to read as they are right now (just big arrays of TRUE and FALSE).

Also, something to consider: clustering the values which compare similarly (like is done on qntm.org/equality) would make the table easier to read as well. (This can be done simply by hand by rearranging the order of headings to bring related values closer together).
up
3
jerryschwartz at comfortable dot com
19 years ago
In some languages, a boolean is promoted to an integer (with a value of 1 or -1, typically) if used in an expression with an integer. I found that PHP has it both ways:

If you add a boolean with a value of true to an integer with a value of 3, the result will be 4 (because the boolean is cast as an integer).

On the other hand, if you test a boolean with a value of true for equality with an integer with a value of three, the result will be true (because the integer is cast as a boolean).

Surprisingly, at first glance, if you use either < or > as the comparison operator the result is always false (again, because the integer as cast as a boolean, and true is neither greater nor less than true).
up
-1
mark at theanti dot social
6 years ago
There is also 0.0 which is not identical to 0.

$x = 0.0;
gettype($x); // double
empty($x); // true
is_null($x); //false
isset($x); // true
is_numeric($x); // true
$x ? true : false; // false
$x == 0; // true
$x == "0"; // true
$x == "0.0"; // true
$x == false; // true
$x == null; // true
$x === 0; // false
$x === false; // false
$x === null; // false
$x === "0"; // false
$x === "0.0"; // false
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