PHP ne requiert pas une définition de type explicite dans les déclarations de variables. Dans ce cas, le type d'une variable est déterminé en fonction de la valeur qu'elle a stocké. C'est-à-dire, si une string est assignée à la variable $var, alors $var est de type string. Si après une valeur int est assignée à $var, elle sera de type int.
PHP peut tenter de convertir le type d'une valeur en une autre automatiquement dans certains contextes. Les différents contextes qui existent sont :
Note: Quand une valeur a besoin d'être interprétée comme un type différent, la valeur elle-même ne change pas de type.
Pour forcer une variable a être évaluée comme un type particulier, voir la section sur le casting de type. Pour changer le type d'une variable, voir la fonction settype().
Ceci est le contexte lors de l'utilisation d' opérateur arithmétique.
Dans ce contexte si un des opérandes est un float (ou pas interprétable comme int), les deux opérandes sont interprétés comme des floats, et le résultat sera un float. Sinon, les opérandes sont interprétés comme des ints, et le résultat sera aussi un int. À partir de PHP 8.0.0, si un des opérandes ne peut être interprété une TypeError est lancée.
Ceci est le contexte lors de l'utilisation de echo, print, l'interpolation de chaînes de caractères, ou l' opérateur de concaténation pour les chaînes de caractères.
Dans ce contexte la valeur sera interprétée comme une string.
Si la valeur ne peut pas être interprétée, une
TypeError est levée.
Antérieur à PHP 7.4.0, une E_RECOVERABLE_ERROR était soulevée.
Ceci est le contexte lors de l'utilisation de déclarations conditionnelles, l'opérateur ternaire, ou un opérateur logique.
Dans ce contexte la valeur sera interprétée comme un bool.
Ceci est le contexte lors de l'utilisation d'un opérateur bit à bit.
Dans ce contexte si tous les opérandes sont de type string alors le résultat sera aussi une string. Sinon, les opérandes seront interprétés comme des ints, et le résultat sera aussi un int. À partir de PHP 8.0.0, si un des opérandes ne peut être interprétés une TypeError est lancée.
Ceci est le contexte lors de l'utilisation d'un opérateur de comparaison.
Les conversions de types qui se produisent dans ce contexte sont expliqués dans le tableau Comparaison avec plusieurs types.
Ceci est le contexte quand une valeur est passée à un paramètre ou propriété typée ou retournée depuis une fonction qui déclare un type de retour.
Dans ce contexte, la valeur doit être une valeur du type. Il existe deux exceptions, la première est la suivante : si la valeur est de type int et que le type déclaré est float, alors l'entier est converti en nombre à virgule flottante. La seconde est : si le type déclaré est un type scalaire , la valeur est convertible en un type scalaire, et le mode de typage coercitif est actif (par défaut), la valeur peut être convertie en une valeur scalaire acceptée. Voir ci-dessous pour une description de ce comportement.
Les fonctions internes
contraigne automatiquement null aux types scalaires,
ce comportement est OBSOLÈTE à partir de PHP 8.1.0.
Lorsque strict_types n’est pas activé, les
déclarations de type scalaire sont soumises à des contraintes de type
implicites limitées.
Si le type exact de la valeur ne fait pas partie de l’union, le type cible
est choisi dans l’ordre de préférence suivant :
À titre d’exception, si la valeur est une chaîne et que int et float font
tous deux partie de l’union, le type préféré est déterminé par la
sémantique de chaîne numérique.
Par exemple, pour "42" int est choisi,
tandis que pour "42.0" float est choisi.
Note:
Les types qui ne font pas partie de la liste de préférences ci-dessus ne sont pas des cibles admissibles à la coercition implicite. En particulier, aucune contrainte implicite aux types
nulletfalsene se produit.
Exemple #1 Exemple de types contraints à une partie type de l'union
<?php
// int|string
42 --> 42 // exact type
"42" --> "42" // exact type
new ObjectWithToString --> "Result of __toString()"
// object never compatible with int, fall back to string
42.0 --> 42 // float compatible with int
42.1 --> 42 // float compatible with int
1e100 --> "1.0E+100" // float too large for int type, fall back to string
INF --> "INF" // float too large for int type, fall back to string
true --> 1 // bool compatible with int
[] --> TypeError // array not compatible with int or string
// int|float|bool
"45" --> 45 // int numeric string
"45.0" --> 45.0 // float numeric string
"45X" --> true // not numeric string, fall back to bool
"" --> false // not numeric string, fall back to bool
"X" --> true // not numeric string, fall back to bool
[] --> TypeError // array not compatible with int, float or bool
?>
Le casting de type converti la valeur à un type donnée en écrivant le type entre parenthèse avant la valeur à convertir.
<?php
$foo = 10; // $foo is an integer
$bar = (bool) $foo; // $bar is a boolean
?>
Les casts permis sont :
(int) - cast en int(bool) - cast en bool(float) - cast en float(string) - cast en string(array) - cast en array(object) - cast en object(unset) - cast en NULLNote:
(integer)est un alias du cast(int).(boolean)est un alias du cast(bool).(binary)est un alias du cast(string).(double)et(real)sont des alias du cast(float). Ces casts n'utilisent pas le nom de type canonique et ne sont pas recommandés.
L'alias de cast (real) est obsolète à partir de PHP 8.0.0.
Le cast (unset) a été rendu obsolète à partir de PHP 7.2.0.
À noter que le cast (unset) est identique à assigner la
valeur NULL à une variable ou un appel.
Le cast (unset) est supprimé à partir de PHP 8.0.0.
Le cast (binary) et le préfixe b
existent uniquement pour la compatibilité ascendante. Actuellement
(binary) et (string) sont identiques,
mais ceci peut changer : vous ne devriez pas compter dessus.
Note:
Les espaces blancs sont ignoré à l'intérieur des parenthèses d'un cast. Ansi, les deux casts suivant sont équivalents :
<?php
$foo = (int) $bar;
$foo = ( int ) $bar;
?>
Cast de strings littérales et variables en strings binaires :
<?php
$binary = (binary) $string;
$binary = b"binary string";
?>
Note: Au lieu de transtyper une variable en une string, il est également possible d'entourer la variable de guillemets doubles.
<?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";
}
?>
Ce qui se produira exactement lors d'un transtypage entre certains types n'est pas forcément évident. Pour plus d'informations, voir ces sections :
Note: Comme PHP prend en charge l'indexation dans les strings via des positions en utilisant la même syntaxe que l'indexation des array, l'exemple suivant est valable pour toutes les versions de PHP :
Voir la section sur l'accès aux chaînes par caractère pour plus d'informations.<?php
$a = 'car'; // $a est une chaîne de caractères
$a[0] = 'b'; // $a est toujours une chaîne de caractères
echo $a; // bar
?>
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 $quotient; // 0.66666666666667
Cast operators have a very high precedence, for example (int)$a/$b is evaluated as ((int)$a)/$b, not as (int)($a/$b) [which would be like intdiv($a,$b) if both $a and $b are integers].
The only exceptions (as of PHP 8.0) are the exponentiation operator ** [i.e. (int)$a**$b is evaluated as (int)($a**$b) rather than ((int)$a)**$b] and the special access/invocation operators ->, ::, [] and () [i.e. in each of (int)$a->$b, (int)$a::$b, (int)$a[$b] and (int)$a($b), the cast is performed last on the result of the variable expression].
"An example of PHP's automatic type conversion is the multiplication 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."
I understand what the doc is trying to say here, but this sentence is not correct as stated, other types can be coerced into floats.
e.g.
<?php
$a = "1.5"; // $a is a string
$b = 100; // $b is an int
$c = $a * $b; // $c is a float, value is 150
// multiplication resulted in a float despite fact that neither operand was a float
Casting objects to arrays is a pain. Example:
<?php
class MyClass {
private $priv = 'priv_value';
protected $prot = 'prot_value';
public $pub = 'pub_value';
public $MyClasspriv = 'second_pub_value';
}
$test = new MyClass();
echo '<pre>';
print_r((array) $test);
/*
Array
(
[MyClasspriv] => priv_value
[*prot] => prot_value
[pub] => pub_value
[MyClasspriv] => second_pub_value
)
*/
?>
Yes, that looks like an array with two keys with the same name and it looks like the protected field was prepended with an asterisk. But that's not true:
<?php
foreach ((array) $test as $key => $value) {
$len = strlen($key);
echo "{$key} ({$len}) => {$value}<br />";
for ($i = 0; $i < $len; ++$i) {
echo ord($key[$i]) . ' ';
}
echo '<hr />';
}
/*
MyClasspriv (13) => priv_value
0 77 121 67 108 97 115 115 0 112 114 105 118
*prot (7) => prot_value
0 42 0 112 114 111 116
pub (3) => pub_value
112 117 98
MyClasspriv (11) => second_pub_value
77 121 67 108 97 115 115 112 114 105 118
*/
?>
The char codes show that the protected keys are prepended with '\0*\0' and private keys are prepended with '\0'.__CLASS__.'\0' so be careful when playing around with this.
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"
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)
The object casting methods presented here do not take into account the class hierarchy of the class you're trying to cast your object into.
/**
* Convert an object to a specific class.
* @param object $object
* @param string $class_name The class to cast the object to
* @return object
*/
public static function cast($object, $class_name) {
if($object === false) return false;
if(class_exists($class_name)) {
$ser_object = serialize($object);
$obj_name_len = strlen(get_class($object));
$start = $obj_name_len + strlen($obj_name_len) + 6;
$new_object = 'O:' . strlen($class_name) . ':"' . $class_name . '":';
$new_object .= substr($ser_object, $start);
$new_object = unserialize($new_object);
/**
* The new object is of the correct type but
* is not fully initialized throughout its graph.
* To get the full object graph (including parent
* class data, we need to create a new instance of
* the specified class and then assign the new
* properties to it.
*/
$graph = new $class_name;
foreach($new_object as $prop => $val) {
$graph->$prop = $val;
}
return $graph;
} else {
throw new CoreException(false, "could not find class $class_name for casting in DB::cast");
return false;
}
}
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!
There are some shorter and faster (at least on my machine) ways to perform a type cast.
<?php
$string='12345.678';
$float=+$string;
$integer=0|$string;
$boolean=!!$string;
?>
Value of uninitialized variable of different data types.
settype($a,'bool');
var_dump($a); //boolean false
settype($b,'string');
var_dump($b); //string '' (length=0)
settype($c,'array');
var_dump($c); //array (size=0) empty
settype($d,'int');
var_dump($d); //int 0
settype($e,'float');
var_dump($e); //float 0
settype($f,'object');
var_dump($f); //object(stdClass)[1]
You REALLY must be aware what you are doing, when you cast a lot in your code. For example, you can accidentaly change FALSE to TRUE (probably not in one line, like here):
if(TRUE === (boolean) (array) (int) FALSE) {
kaboom();
}
in response to bhsmither at gmail.com
It raises a warning because of the bad enquoted variable
<?php
error_reporting( E_ALL | E_STRICT );
$foo['ten'] = 10; // $foo['ten'] is an array holding an integer at key "ten"
$str = "{$foo['ten']}"; // works "10"
$str = "$foo[ten]"; // DO NOT work!
Type casting from string to int and vice versa is probably the most common conversation. PHP does this very simply through the +. and .= operators, removing any explicit casting:
<?php
$x = 1;
var_dump($x); // int(1)
$x .= 1;
var_dump($x); // string(2) "11"; also an empty string ("") would cast to string without changing $x
$x = "1";
var_dump($x); // string(1) "1"
$x += 1;
var_dump($x); // int(2); also a zero value (0) would cast to int without changing $x
?>
namaroulis stated "I found it tricky to check if a posted value was an integer"; to test if a variable is a number or a numeric string (such as form input, which is always a string), you must use is_numeric():
<?php
$_POST['a'] = "42";
is_numeric( $_POST['a'] ); // true
?>
Cast a string to binary using PHP < 5.2.1
$binary = unpack('c*', $string);
I found it tricky to check if a posted value was an integer.
<?php
$_POST['a'] = "42";
is_int( $_POST['a'] ); //false
is_int( intval( "anything" ) ); //always true
?>
A method I use for checking if a string represents an integer value.
<?php
function check_int( $str )
{
return is_numeric( $str ) && intval( $str ) - $str == 0;
}
?>
<?php
$foo['ten'] = 10; // $foo['ten'] is an array holding an integer at key "ten"
$str = "$foo['ten']"; // throws T_ENCAPSED_AND_WHITESPACE error
$str = "$foo[ten]"; // works because constants are skipped in quotes
$fst = (string) $foo['ten']; // works with clear intention
?>
It seems (unset) is pretty useless. But for people who like to make their code really compact (and probably unreadable). You can use it to use an variable and unset it on the same line:
Without cast:
<?php
$hello = 'Hello world';
print $hello;
unset($hello);
?>
With the unset cast:
<?php
$hello = 'Hello world';
$hello = (unset) print $hello;
?>
Hoorah, we lost another line!
It would be useful to know the precedence (for lack of a better word) for type juggling. This entry currently explains that "if either operand is a float, then both operands are evaluated as floats, and the result will be a float" but could (and I think should) provide a hierarchy that indicates, for instance, "between an int and a boolean, int wins; between a float and an int, float wins; between a string and a float, string wins" and so on (and don't count on my example accurately capturing the true hierarchy, as I haven't actually done the tests to figure it out). Thanks!
May be expected, but not stated ..
Casting to the existing (same) type has no effect.
$t = 'abc'; // string 'abc'
$u=(array) $t; // array 0 => string 'abc' <-- now an array
$v=(array) $u; // array 0 => string 'abc' <-- unchanged
@alexgr (20-Jun-2008)
Correct me if I'm wrong, but that is not a cast, it might be useful sometimes, but the IDE will not reflect what's really happening:
<?php
class MyObject {
/**
* @param MyObject $object
* @return MyObject
*/
static public function cast(MyObject $object) {
return $object;
}
/** Does nothing */
function f() {}
}
class X extends MyObject {
/** Throws exception */
function f() { throw new exception(); }
}
$x = MyObject::cast(new X);
$x->f(); // Your IDE tells 'f() Does nothing'
?>
However, when you run the script, you will get an exception.
In my much of my coding I have found it necessary to type-cast between objects of different class types.
More specifically, I often want to take information from a database, convert it into the class it was before it was inserted, then have the ability to call its class functions as well.
The following code is much shorter than some of the previous examples and seems to suit my purposes. It also makes use of some regular expression matching rather than string position, replacing, etc. It takes an object ($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)));
}
}
WHERE'S THE BEEF?
Looks like type-casting user-defined objects is a real pain, and ya gotta be nuttin' less than a brain jus ta cypher-it. But since PHP supports OOP, you can add the capabilities right now. Start with any simple class.
<?php
class Point {
protected $x, $y;
public function __construct($xVal = 0, $yVal = 0) {
$this->x = $xVal;
$this->y = $yVal;
}
public function getX() { return $this->x; }
public function getY() { return $this->y; }
}
$p = new Point(25, 35);
echo $p->getX(); // 25
echo $p->getY(); // 35
?>
Ok, now we need extra powers. PHP gives us several options:
A. We can tag on extra properties on-the-fly using everyday PHP syntax...
$p->z = 45; // here, $p is still an object of type [Point] but gains no capability, and it's on a per-instance basis, blah.
B. We can try type-casting it to a different type to access more functions...
$p = (SuperDuperPoint) $p; // if this is even allowed, I doubt it. But even if PHP lets this slide, the small amount of data Point holds would probably not be enough for the extra functions to work anyway. And we still need the class def + all extra data. We should have just instantiated a [SuperDuperPoint] object to begin with... and just like above, this only works on a per-instance basis.
C. Do it the right way using OOP - and just extend the Point class already.
<?php
class Point3D extends Point {
protected $z; // add extra properties...
public function __construct($xVal = 0, $yVal = 0, $zVal = 0) {
parent::__construct($xVal, $yVal);
$this->z = $zVal;
}
public function getZ() { return $this->z; } // add extra functions...
}
$p3d = new Point3D(25, 35, 45); // more data, more functions, more everything...
echo $p3d->getX(); // 25
echo $p3d->getY(); // 35
echo $p3d->getZ(); // 45
?>
Once the new class definition is written, you can make as many Point3D objects as you want. Each of them will have more data and functions already built-in. This is much better than trying to beef-up any "single lesser object" on-the-fly, and it's way easier to do.
Re: the typecasting between classes post below... fantastic, but slightly flawed. Any class name longer than 9 characters becomes a problem... SO here's a simple fix:
function typecast($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. ;)
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.
Checking for strings to be integers?
How about if a string is a float?
<?php
/* checks if a string is an integer with possible whitespace before and/or after, and also isolates the integer */
$isInt=preg_match('/^\s*([0-9]+)\s*$/', $myString, $myInt);
echo 'Is Integer? ', ($isInt) ? 'Yes: '.$myInt[1] : 'No', "\n";
/* checks if a string is an integer with no whitespace before or after */
$isInt=preg_match('/^[0-9]+$/', $myString);
echo 'Is Integer? ', ($isInt) ? 'Yes' : 'No', "\n";
/* When checking for floats, we assume the possibility of no decimals needed. If you MUST require decimals (forcing the user to type 7.0 for example) replace the sequence:
[0-9]+(\.[0-9]+)?
with
[0-9]+\.[0-9]+
*/
/* checks if a string is a float with possible whitespace before and/or after, and also isolates the number */
$isFloat=preg_match('/^\s*([0-9]+(\.[0-9]+)?)\s*$/', $myString, $myNum);
echo 'Is Number? ', ($isFloat) ? 'Yes: '.$myNum[1] : 'No', "\n";
/* checks if a string is a float with no whitespace before or after */
$isInt=preg_match('/^[0-9]+(\.[0-9]+)?$/', $myString);
echo 'Is Number? ', ($isFloat) ? 'Yes' : 'No', "\n";
?>
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.
The code listed in some of the comments here for supposedly "casting" from one class to another using unserialize/serialize does not actually change the class of the existing object; it creates a new object. So it's not the same as a cast.
(array) null
array(null)
are not the same.
var_dump((array) null) =>
array (size=0)
empty
var_dump(array (null)) =>
array (size=1)
0 => null
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 $b: b
For some reason the code-fix posted by philip_snyder at hotmail dot com [27-Feb-2004 02:08]
didn't work for me neither with long_class_names nor with short_class_names. I'm using PHP v4.3.5 for Linux.
Anyway here's what I wrote to solve the long_named_classes problem:
<?php
function typecast($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;
}
}
?>
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
Just a little experiment on the (unset) type cast:
<?php
$var = 1;
$var_unset = (unset) $var;
$var_ref_unset &= (unset) $var;
var_dump($var);
var_dump($var_unset);
var_dump($var_ref_unset);
?>
output:
int(1)
NULL
int(0)
Type Juggling<br/>
<?php $count = "2 cats"; ?>
Type: <?php echo gettype($count); ?><br/>
<?php $count += 3; ?>
Type: <?php echo gettype($count); ?><br/>
<?php $cats = "I have " . $count . "cats."; ?>
Cats: <?php echo gettype($cats); ?><br/>
<br/>
Type Casting<br/>
<?php settype($count, "integer"); ?>
count: <?php echo gettype($count); ?><br/>
<?php $count2 = (string)$count; ?>
count: <?php echo gettype($count); ?><br/>
count2: <?php echo gettype($count2); ?><br/>
<?php $test1 = 3; ?>
<?php $test2 = 3; ?>
<?php settype($test1, "string"); ?>
<?php (string)$test2; ?>
test1: <?php echo gettype($test1); ?><br/>
test2: <?php echo gettype($test2); ?><br/>
json_decode users consider this, when casting stdClass to array:
<?php
$obj = new stdClass();
$obj->{"2"} = "id";
$arr = (array) $obj;
$result = isset($arr["2"]) || array_key_exists(2, $arr); // false
?>
..though casting is at least 2x faster than foreach.
IMAGINATION REQUIRED...
We can be a witness to PHP's 'type-jugglin' in real-time with a simple implementation of a MemoryMap. For the sake our purposes, pretend that this is an empty MemoryMap.
+-------+------+------+-------+
| index | $var | type | value |
+-------+------+------+-------+
| 1 | --- | NULL | null |
| 2 | --- | NULL | null |
| 3 | --- | NULL | null |
| 4 | --- | NULL | null |
+-------+------+------+-------+
<?php
# create some variables...
$a = 10;
$b = "Hello";
$c = array(55.45, 98.65);
# Now look at map...
?>
+-------+-------+---------+--------+
| index | $var | type | value |
+-------+-------+---------+--------+
| 1 | $a | INTEGER | 10 |
| 2 | $b | STRING | Hello |
| 3 | $c[0] | FLOAT | 55.45 |
| 4 | $c[1] | FLOAT | 98.65 |
+-------+-------+---------+--------+
<?php
# Now, change the variable types...
$a = "Bye";
$b = 2;
$c[0] = "Buy";
$c[1] = "Now!";
#Look at map...
?>
+-------+-------+---------+--------+
| index | $var | type | value |
+-------+-------+---------+--------+
| 1 | $a | STRING | Bye | <- used to be INTEGER
| 2 | $b | INTEGER | 2 | <- used to be STRING
| 3 | $c[0] | STRING | Buy | <- used to be FLOAT
| 4 | $c[1] | STRING | Right | <- used to be FLOAT
+-------+-------+---------+--------+
