#45207 [Opn->Csd]: Incorrect or missing documentation for languages.variables

ID: 45207 Updated by: ross@php.net Reported By: chrisvroberts at gmail dot com -Status: Open +Status: Closed Bug Type: Documentation problem Operating System: n/a PHP Version: Irrelevant Assigned To: ross New Comment: This bug has been fixed in the documentation's XML sources. Since the online and downloadable versions of the documentation need some time to get updated, we would like to ask you to be a bit patient. Thank you for the report, and for helping us make our documentation better. Previous Comments: ------------------------------------------------------------------------ [2008-10-08 19:31:49] ross@php.net PHP is not a fully typed language, because of this variables' types are only used depending on the context in which they are referred to. I have a rather lengthy example to explain this (see below) but I'll try to trim that down before it's committed. // Example: <?php // Unset variable; outputs NULL var_dump($unset_var); // Boolean usage; outputs 'false' echo("Boolean\n"); // See ternary operators for more on this syntax echo($unset_bool ? "true\n" : "false\n"); echo("\n"); // String usage; outputs 'string(3) "abc"' echo("String\n"); $unset_str .= 'abc'; var_dump($unset_str); echo("\n"); // Integer usage; outputs 'int(25)' echo("Integer\n"); $unset_int += 25; // 0 + 25 => 25 var_dump($unset_int); echo("\n"); // Float/double usage; outputs 'float(1.25)' echo("Float\n"); $unset_float += 1.25; var_dump($unset_float); echo("\n"); // Array usage; outputs array(1) { [3]=> string(3) "def" } echo("Array\n"); $unset_arr[3] = "def"; // array() + array(3 => "def") => array(3 => "def") var_dump($unset_arr); echo("\n"); // Object usage; creates new stdClass object (see http://www.php.net/manual/en/reserved.classes.php) // Outputs: // object(stdClass)#1 (1) { // ["foo"]=> // string(3) "bar" // } echo("Object\n"); $unset_obj->foo = 'bar'; var_dump($unset_obj); echo("\n"); ?> ------------------------------------------------------------------------ [2008-06-08 12:13:23] chrisvroberts at gmail dot com Description: ------------ On "http://www.php.net/manual/en/language.variables.php", it says: "It is not necessary to initialize variables in PHP however it is a very good practice. Uninitialized variables have a default value of their type - FALSE, zero, empty string or an empty array." However, I was unable to find in the documentation how to define a variable and specify it's type without assigning a value to it. When a variable is declared and not initialized, which of the values described above would the variable take. If it is used in a context which specifies say boolean, then value would be FALSE but if it is used in an overloaded context, which value would it take and is there a precedence? Is this implementaitn rather than language specific? If it is possible to specify a variables type without assigning to it, perhaps this should be described in the documentation in order to put the above quote into context? ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=45207&edit=1