Web студия "GrandView"

Следующие таблицы демонстрируют работу PHP с типами переменных и операторами сравнения, как в случае свободного, так и в случае строгого сравнения. Также эта информация относится к разделу документации по приведению типов. Вдохновением на создание этого раздела мы обязаны различным комментариям пользователей и работе над BlueShoes.

До осмотра таблиц, важно знать и понимать типы переменных и их значения. К примеру, "42" -- строка, в то время как 42 -- целое. FALSE -- логическое, а "false" -- строка.

Таблица P-1. Сравнение типов $x и результатов функций PHP, связанных с типами

Выражение	gettype()	empty()	is_null()	isset()	логическое : `if($x)`
`$x = "";`	строка	`TRUE`	`FALSE`	`TRUE`	`FALSE`
`$x = NULL`	NULL	`TRUE`	`TRUE`	`FALSE`	`FALSE`
`var $x;`	NULL	`TRUE`	`TRUE`	`FALSE`	`FALSE`
`$x` неопределена	NULL	`TRUE`	`TRUE`	`FALSE`	`FALSE`
`$x = array();`	массив	`TRUE`	`FALSE`	`TRUE`	`FALSE`
`$x = false;`	логическое	`TRUE`	`FALSE`	`TRUE`	`FALSE`
`$x = true;`	логическое	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = 1;`	целое	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = 42;`	целое	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = 0;`	целое	`TRUE`	`FALSE`	`TRUE`	`FALSE`
`$x = -1;`	целое	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = "1";`	строка	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = "0";`	строка	`TRUE`	`FALSE`	`TRUE`	`FALSE`
`$x = "-1";`	строка	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = "php";`	строка	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = "true";`	строка	`FALSE`	`FALSE`	`TRUE`	`TRUE`
`$x = "false";`	строка	`FALSE`	`FALSE`	`TRUE`	`TRUE`

Таблица P-2. Гибкое сравнение с помощью ==

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

Таблица P-3. Жёсткое сравнение с помощью ===

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

add a note User Contributed Notes
Таблица сравнения типов в PHP

frank
14-Aug-2007 03:06


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-Mar-2007 03:06


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-Aug-2006 11:32


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-Dec-2005 11:23


Note that php comparison is not transitive:



"php" == 0 => true

0 == null => true

null == "php" => false

php [at] barryhunter [.] co [.] uk
07-Sep-2005 12:44


In case it helps someone, here's a table to compare different Variable tests (created before I found this page!)



http://www.deformedweb.co.uk/php_variable_tests.php

jerryschwartz at comfortable dot com
26-Jul-2005 01:04


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-Jun-2005 02:27


<?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-Jan-2005 07:00


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.

add a note

Приложение P. Таблица сравнения типов в PHP