PHP type comparison tables

Die folgenden Tabellen zeigen das Verhalten von Typen und Vergleichsoperatoren in PHP, sowohl für schwach und stark typisierte Vergleiche. Dieser Anhang steht im Zusammenhang mit dem Abschnitt zu Type juggling. Anregungen für diesen Abschnitt kamen aus verschiedenen Benuterkommentaren und der Arbeit von » BlueShoes.

Bevor diese Tabellen verwendet werden ist es wichtig die Typen und ihre Bedeutungen zu verstehen. "42" ist zum Beispiel ein string, während 42 ein integer ist. FALSE ist ein boolean, obwohl "false" ein string ist.

Hinweis:
HTML-Formulare übergeben keine integer, float oder boolesche Werte, sie übertragen strings. Um herauszufinden, ob ein string numerisch ist kann man is_numeric() verwenden.

Hinweis:
Wenn man einfach if ($x) verwendet, obwohl $x undefiniert ist, so wird ein Fehler der Stufe E_NOTICE erzeugt. Verwenden sie stattdessen empty() oder isset() und/oder initialisiere sie die verwendeten Variablen.

Vergleiche von $x mittels PHP-Funktionen

Ausdruck gettype() empty() is_null() isset() boolean : if($x)

$x = ""; string TRUE FALSE TRUE FALSE

$x = null NULL TRUE TRUE FALSE FALSE

var $x; NULL TRUE TRUE FALSE FALSE

$x ist undefiniert NULL TRUE TRUE FALSE FALSE

$x = array(); array TRUE FALSE TRUE FALSE

$x = false; boolean TRUE FALSE TRUE FALSE

$x = true; boolean FALSE FALSE TRUE TRUE

$x = 1; integer FALSE FALSE TRUE TRUE

$x = 42; integer FALSE FALSE TRUE TRUE

$x = 0; integer TRUE FALSE TRUE FALSE

$x = -1; integer 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

**Vergleiche von `$x` mittels PHP-Funktionen**
Ausdruck	gettype()	empty()	is_null()	isset()	boolean : if($x)
$x = "";	string	`TRUE`	`FALSE`	`TRUE`	`FALSE`
$x = null	NULL	`TRUE`	`TRUE`	`FALSE`	`FALSE`
var $x;	NULL	`TRUE`	`TRUE`	`FALSE`	`FALSE`
`$x` ist undefiniert	NULL	`TRUE`	`TRUE`	`FALSE`	`FALSE`
$x = array();	array	`TRUE`	`FALSE`	`TRUE`	`FALSE`
$x = false;	boolean	`TRUE`	`FALSE`	`TRUE`	`FALSE`
$x = true;	boolean	`FALSE`	`FALSE`	`TRUE`	`TRUE`
$x = 1;	integer	`FALSE`	`FALSE`	`TRUE`	`TRUE`
$x = 42;	integer	`FALSE`	`FALSE`	`TRUE`	`TRUE`
$x = 0;	integer	`TRUE`	`FALSE`	`TRUE`	`FALSE`
$x = -1;	integer	`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`

Typschwache Vergleiche mittels ==

TRUE FALSE 1 0 -1 "1" "0" "-1" NULL array() "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 TRUE TRUE

-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

array() FALSE TRUE FALSE FALSE FALSE FALSE FALSE FALSE TRUE TRUE FALSE FALSE

"php" TRUE FALSE FALSE TRUE FALSE FALSE FALSE FALSE FALSE FALSE TRUE FALSE

"" FALSE TRUE FALSE TRUE FALSE FALSE FALSE FALSE TRUE FALSE FALSE TRUE

**Typschwache Vergleiche mittels ==**
	`TRUE`	`FALSE`	1	0	-1	"1"	"0"	"-1"	`NULL`	array()	"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`	`TRUE`	`TRUE`
-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`
array()	`FALSE`	`TRUE`	`FALSE`	`FALSE`	`FALSE`	`FALSE`	`FALSE`	`FALSE`	`TRUE`	`TRUE`	`FALSE`	`FALSE`
"php"	`TRUE`	`FALSE`	`FALSE`	`TRUE`	`FALSE`	`FALSE`	`FALSE`	`FALSE`	`FALSE`	`FALSE`	`TRUE`	`FALSE`
""	`FALSE`	`TRUE`	`FALSE`	`TRUE`	`FALSE`	`FALSE`	`FALSE`	`FALSE`	`TRUE`	`FALSE`	`FALSE`	`TRUE`

Typstarke Vergleiche mittels ===

TRUE FALSE 1 0 -1 "1" "0" "-1" NULL array() "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

array() 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

Typstarke Vergleiche mittels *===*
	`TRUE`	`FALSE`	1	0	-1	"1"	"0"	"-1"	`NULL`	array()	"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`
array()	`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`

12 BenutzerBeiträge:
- Beiträge aktualisieren...

php at benizi dot com
15.02.2010 19:31


It's interesting to note that 'empty()' and 'boolean : if($x)'

are paired as logical opposites, as are 'is_null()' and 'isset()'.

edgar at goodforall dot eu
15.12.2009 15:55


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);

}



?>

rich
8.05.2008 16:20


The note about object comparison should be corrected. Cloning objects does not imply instances are the same, so === would return FALSE. 



Compare object

<?php

$o = new stdClass();

$o->we = 12;



$o2 = new stdClass();

$o2->we = 12;



$o3 = clone $o2;

var_dump($o == $o2); //true

var_dump($o === $o2); //false

var_dump($o3 === $o2); //false

?>

gernovich at ya dot ru
8.05.2008 9:48


Universal comparison test.



<?php



$tests = array();

$tests['==']  = create_function('$a, $b', 'return $a==$b;');

$tests['==='] = create_function('$a, $b', 'return $a===$b;');

$tests['!='] = create_function('$a, $b', 'return $a!=$b;');

$tests['<>'] = create_function('$a, $b', 'return $a<>$b;');

$tests['!=='] = create_function('$a, $b', 'return $a!==$b;');

$tests['<']   = create_function('$a, $b', 'return $a<$b;');

$tests['>']   = create_function('$a, $b', 'return $a>$b;');

$tests['<=']  = create_function('$a, $b', 'return $a<=$b;');

$tests['>=']  = create_function('$a, $b', 'return $a>=$b;');



$comparison = array();

$comparison['TRUE'] = true;

$comparison['FALSE'] = false;

$comparison['1'] = 1;

$comparison['0'] = 0;

$comparison['-1'] = -1;

$comparison['3,14'] = pi();

$comparison['"1"'] = '1';

$comparison['"0"'] = '0';

$comparison['"-1"'] = '-1';

$comparison['NULL'] = null;

$comparison['array()'] = array();

$comparison['"php"'] = 'php';

        

print '<h1>PHP version '.PHP_VERSION.' type comparison tables</h1>';

        

foreach ($tests as $test=>$function) {

    print "<h2>Comparisons with $test</h2>";

    print "<table border='1'>";

    print "<tr>";

    print "<th>&nbsp;</th>";

    foreach (array_keys($comparison) as $name) {

        print "<th>$name</th>";

    }

    print "</tr>";

    foreach ($comparison as $arg_1_name => $arg_1_value) {

        print '<tr>';

        print "<th>$arg_1_name</th>";

        foreach ($comparison as $arg_2_value) {

            print '<td>';

            print $function($arg_1_value, $arg_2_value)==true ?

                        '<span style="color:#00F;">TRUE</span>' : '<span style="color:#F00;">FALSE</span>';

            print '</td>';

        }

        print "</tr>";

    }

    print "</table>";

}



?>

info at shaelf dot ru
6.01.2008 22:51


Compare object

<?php

$o = new stdClass();

$o->we = 12;



$o2 = new stdClass();

$o2->we = 12;



$o3 = clone $o2;

var_dump($o == $o2); //true

var_dump($o === $o2); //false

var_dump($o3 === $o2); //true

?>

frank
15.08.2007 0:06


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...).

15.03.2007 23:06


Re: omit's comment



The note omit quotes is referring to the VALUE returned, not its name. If you put 42 into a text field, the corresponding array value will be the string "42". The note makes no comment on the array's keys.

omit
23.08.2006 20:32


the manual said "HTML Forms do not pass integers, floats, or booleans; they pass strings"



while this is true, php will sometimes change the type to either type array, or possibly type integer(no, not a numeric string) if it was used as an array key. php seems to do this when it parses the request data into the predefined variable arrays.



example:



<input type="text" name="foo[5]">

<input type="text" name="foo[7]">



now obviously the browser will send those names as a string. but php will change thier type.



<?php



// $_POST['foo'] is an array

var_dump($_POST['foo']);



foreach ($_POST['foo'] as $key => $val) {

    // the keys 5 and 7 will be type integer

    var_dump($key);

}



?>



because of this, its also a good idea to check the types of your variables.

Jan
29.12.2005 20:23


Note that php comparison is not transitive:



"php" == 0 => true

0 == null => true

null == "php" => false

jerryschwartz at comfortable dot com
26.07.2005 22:04


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).

tom
17.06.2005 11:27


<?php


if (strlen($_POST['var']) > 0) {


    // form value is ok


}


?>





When working with HTML forms this a good way to:





(A) let "0" post values through like select or radio values that correspond to array keys or checkbox booleans that would return FALSE with empty(), and;


(B) screen out $x = "" values, that would return TRUE with isset()!





Because HTML forms post values as strings, this is a good way to test variables!





[[Editor Note: This will create a PHP Error of level E_NOTICE if the checked variable (in this case $_POST['var']) is undefined. It may be used after (in conjuection with) isset() to prevent this.]]

aidan at php dot net
24.01.2005 16:00


The way PHP handles comparisons when multiple types are concerned is quite confusing.



For example:

"php" == 0



This is true, because the string is casted interally to an integer. Any string (that does not start with a number), when casted to an integer, will be 0.

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PHP type comparison tables