Types
For a Cast to a User Defined Object you can define a cast method:
class MyObject {
/**
* @param MyObject $object
* @return MyObject
*/
static public function cast(MyObject $object) {
return $object;
}
}
In your php page code you can:
$myObject = MyObject::cast($_SESSION["myObject"]);
Then, PHP will validate the value and your IDE will help you.
Type Juggling
PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which the variable is used. That is to say, if a string value is assigned to variable $var, $var becomes a string. If an integer value is then assigned to $var, it becomes an integer.
An example of PHP's automatic type conversion is the addition operator '+'. If either operand is a float, then both operands are evaluated as floats, and the result will be a float. Otherwise, the operands will be interpreted as integers, and the result will also be an integer. Note that this does not change the types of the operands themselves; the only change is in how the operands are evaluated and what the type of the expression itself is.
<?php
$foo = "0"; // $foo is string (ASCII 48)
$foo += 2; // $foo is now an integer (2)
$foo = $foo + 1.3; // $foo is now a float (3.3)
$foo = 5 + "10 Little Piggies"; // $foo is integer (15)
$foo = 5 + "10 Small Pigs"; // $foo is integer (15)
?>
If the last two examples above seem odd, see String conversion to numbers.
To force a variable to be evaluated as a certain type, see the section on Type casting. To change the type of a variable, see the settype() function.
To test any of the examples in this section, use the var_dump() function.
Note: The behaviour of an automatic conversion to array is currently undefined.
Also, because PHP supports indexing into strings via offsets using the same syntax as array indexing, the following example holds true for all PHP versions:
See the section titled String access by character for more information.<?php
$a = 'car'; // $a is a string
$a[0] = 'b'; // $a is still a string
echo $a; // bar
?>
Type Casting
Type casting in PHP works much as it does in C: the name of the desired type is written in parentheses before the variable which is to be cast.
<?php
$foo = 10; // $foo is an integer
$bar = (boolean) $foo; // $bar is a boolean
?>
The casts allowed are:
- (int), (integer) - cast to integer
- (bool), (boolean) - cast to boolean
- (float), (double), (real) - cast to float
- (string) - cast to string
- (binary) - cast to binary string (PHP 6)
- (array) - cast to array
- (object) - cast to object
- (unset) - cast to NULL (PHP 5)
(binary) casting and b prefix forward support was added in PHP 5.2.1
Note that tabs and spaces are allowed inside the parentheses, so the following are functionally equivalent:
<?php
$foo = (int) $bar;
$foo = ( int ) $bar;
?>
Casting literal strings and variables to binary strings:
<?php
$binary = (binary)$string;
$binary = b"binary string";
?>
Note: Instead of casting a variable to a string, it is also possible to enclose the variable in double quotes.
<?php
$foo = 10; // $foo is an integer
$str = "$foo"; // $str is a string
$fst = (string) $foo; // $fst is also a string
// This prints out that "they are the same"
if ($fst === $str) {
echo "they are the same";
}
?>
It may not be obvious exactly what will happen when casting between certain types. For more information, see these sections:
add a note
User Contributed NotesType Juggling
alexgr at gmail dot com
20-Jun-2008 06:43
20-Jun-2008 06:43
miracle at 1oo-percent dot de
20-Feb-2006 09:26
20-Feb-2006 09:26
If you want to convert a string automatically to float or integer (e.g. "0.234" to float and "123" to int), simply add 0 to the string - PHP will do the rest.
e.g.
$val = 0 + "1.234";
(type of $val is float now)
$val = 0 + "123";
(type of $val is integer now)
23-Jun-2005 08:47
If you have a boolean, performing increments on it won't do anything despite it being 1. This is a case where you have to use a cast.
<html>
<body> <!-- don't want w3.org to get mad... -->
<?php
$bar = TRUE;
?>
I have <?=$bar?> bar.
<?php
$bar++;
?>
I now have <?=$bar?> bar.
<?php
$bar = (int) $bar;
$bar++;
?>
I finally have <?=$bar?> bar.
</body>
</html>
That will print
I have 1 bar.
I now have 1 bar.
I finally have 2 bar.
toma at smartsemantics dot com
10-Mar-2005 10:24
10-Mar-2005 10:24
In my much of my coding I have found it necessary to type-cast between objects of different class types.
More specifically, I often want to take information from a database, convert it into the class it was before it was inserted, then have the ability to call its class functions as well.
The following code is much shorter than some of the previous examples and seems to suit my purposes. It also makes use of some regular expression matching rather than string position, replacing, etc. It takes an object ($obj) of any type and casts it to an new type ($class_type). Note that the new class type must exist:
function ClassTypeCast(&$obj,$class_type){
if(class_exists($class_type,true)){
$obj = unserialize(preg_replace"/^O:[0-9]+:\"[^\"]+\":/i",
"O:".strlen($class_type).":\"".$class_type."\":", serialize($obj)));
}
}
Raja
10-Feb-2005 07:05
10-Feb-2005 07:05
Uneven division of an integer variable by another integer variable will result in a float by automatic conversion -- you do not have to cast the variables to floats in order to avoid integer truncation (as you would in C, for example):
$dividend = 2;
$divisor = 3;
$quotient = $dividend/$divisor;
print $quotient; // 0.66666666666667
tom5025_ at hotmail dot com
25-Aug-2004 04:27
25-Aug-2004 04:27
function strhex($string)
{
$hex="";
for ($i=0;$i<strlen($string);$i++)
$hex.=dechex(ord($string[$i]));
return $hex;
}
function hexstr($hex)
{
$string="";
for ($i=0;$i<strlen($hex)-1;$i+=2)
$string.=chr(hexdec($hex[$i].$hex[$i+1]));
return $string;
}
to convert hex to str and vice versa
dimo dot vanchev at bianor dot com
10-Mar-2004 11:02
10-Mar-2004 11:02
For some reason the code-fix posted by philip_snyder at hotmail dot com [27-Feb-2004 02:08]
didn't work for me neither with long_class_names nor with short_class_names. I'm using PHP v4.3.5 for Linux.
Anyway here's what I wrote to solve the long_named_classes problem:
<?php
function typecast($old_object, $new_classname) {
if(class_exists($new_classname)) {
$old_serialized_object = serialize($old_object);
$old_object_name_length = strlen(get_class($old_object));
$subtring_offset = $old_object_name_length + strlen($old_object_name_length) + 6;
$new_serialized_object = 'O:' . strlen($new_classname) . ':"' . $new_classname . '":';
$new_serialized_object .= substr($old_serialized_object, $subtring_offset);
return unserialize($new_serialized_object);
} else {
return false;
}
}
?>
philip_snyder at hotmail dot com
27-Feb-2004 11:08
27-Feb-2004 11:08
Re: the typecasting between classes post below... fantastic, but slightly flawed. Any class name longer than 9 characters becomes a problem... SO here's a simple fix:
function typecast($old_object, $new_classname) {
if(class_exists($new_classname)) {
// Example serialized object segment
// O:5:"field":9:{s:5:... <--- Class: Field
$old_serialized_prefix = "O:".strlen(get_class($old_object));
$old_serialized_prefix .= ":\"".get_class($old_object)."\":";
$old_serialized_object = serialize($old_object);
$new_serialized_object = 'O:'.strlen($new_classname).':"'.$new_classname . '":';
$new_serialized_object .= substr($old_serialized_object,strlen($old_serialized_prefix));
return unserialize($new_serialized_object);
}
else
return false;
}
Thanks for the previous code. Set me in the right direction to solving my typecasting problem. ;)
post_at_henribeige_dot_de
04-May-2003 12:37
04-May-2003 12:37
If you want to do not only typecasting between basic data types but between classes, try this function. It converts any class into another. All variables that equal name in both classes will be copied.
function typecast($old_object, $new_classname) {
if(class_exists($new_classname)) {
$old_serialized_object = serialize($old_object);
$new_serialized_object = 'O:' . strlen($new_classname) . ':"' . $new_classname . '":' .
substr($old_serialized_object, $old_serialized_object[2] + 7);
return unserialize($new_serialized_object);
}
else
return false;
}
Example:
class A {
var $secret;
function A($secret) {$this->secret = $secret;}
function output() {echo("Secret class A: " . $this->secret);}
}
class B extends A {
var $secret;
function output() {echo("Secret class B: " . strrev($this->secret));}
}
$a = new A("Paranoia");
$b = typecast($a, "B");
$a->output();
$b->output();
echo("Classname \$a: " . get_class($a) . "Classname \$b: " . get_class($b));
Output of the example code above:
Secret class A: Paranoia
Secret class B: aionaraP
Classname $a: a
Classname $b: b
yury at krasu dot ru
27-Nov-2002 05:24
27-Nov-2002 05:24
incremental operator ("++") doesn't make type conversion from boolean to int, and if an variable is boolean and equals TRUE than after ++ operation it remains as TRUE, so:
$a = TRUE;
echo ($a++).$a; // prints "11"
29-Aug-2002 01:26
Printing or echoing a FALSE boolean value or a NULL value results in an empty string:
(string)TRUE //returns "1"
(string)FALSE //returns ""
echo TRUE; //prints "1"
echo FALSE; //prints nothing!