Enumeration (or enum) is mainly used to assign names to integral constants, the names make a program easy to read and maintain. In PHP, enumeration datatypes can be implemented using and extending abstract classes.
Approach 1: Using simple abstract class to for data member encapsulation.
Example:
<?php // PHP program to show use of enumerations // Encapsulating constants abstract class gfg {
const dummy_string = "geeksforgeeks" ;
const dummy_int = 1;
const dummy_array = array ( 'a' => 1, 'b' => 2);
} $a = gfg::dummy_string;
$b = gfg::dummy_int;
$c = gfg::dummy_array;
var_dump( $a );
var_dump( $b );
var_dump( $c );
?> |
string(13) "geeksforgeeks" int(1) array(2) { ["a"]=> int(1) ["b"]=> int(2) }
Approach 2: Extend an abstract class acting as an enumeration container for encapsulating constants.
Example:
<?php // PHP program to show use of enumerations // Base enumeration class abstract class enum {
// Enumeration constructor
final public function __construct( $value ) {
$this ->value = $value ;
}
// String representation
final public function __toString() {
return $this ->value;
}
} // Encapsulating enumerated constants class gfg extends enum {
const dummy_string = "geeksforgeeks" ;
const dummy_int = 1;
const dummy_array = array ( 'a' => 1, 'b' => 2);
} $a = new gfg(gfg::dummy_string);
$b = new gfg(gfg::dummy_int);
$c = new gfg(gfg::dummy_array);
var_dump( $a );
var_dump( $b );
var_dump( $c );
?> |
object(gfg)#1 (1) { ["value"]=> string(13) "geeksforgeeks" } object(gfg)#2 (1) { ["value"]=> int(1) } object(gfg)#3 (1) { ["value"]=> array(2) { ["a"]=> int(1) ["b"]=> int(2) } }
Approach 3: Enumeration mentioned in the previous approach can be specialized by addition of validity checks and exception handling for more flexible usage of enumeration datatype.
Example:
<?php // PHP program to show use of enumerations // Base enumeration class abstract class enum {
// Enumeration constructor
final public function __construct( $value ) {
try {
$c = new ReflectionClass( $this );
// Content validation
if (!in_array( $value , $c ->getConstants())) {
try {
throw new Exception( "IllegalArgumentException" );
}
catch (Exception $k ) {
echo $k ->getMessage();
}
}
$this ->value = $value ;
}
catch (Exception $k ){
echo $k ->getMessage();
}
}
// String representation
final public function __toString() {
return $this ->value;
}
} // Encapsulating enumerated constants class gfg extends enum {
const dummy_string = "geeksforgeeks" ;
const dummy_int = 1;
const dummy_array = array ( 'a' => 1, 'b' => 2);
} $a = new gfg(gfg::dummy_string);
$b = new gfg(gfg::dummy_int);
$c = new gfg(gfg::dummy_array);
$d = new gfg(3.14);
var_dump( $a );
var_dump( $b );
var_dump( $c );
var_dump( $d );
?> |
IllegalArgumentExceptionobject(gfg)#1 (1) { ["value"]=> string(13) "geeksforgeeks" } object(gfg)#2 (1) { ["value"]=> int(1) } object(gfg)#3 (1) { ["value"]=> array(2) { ["a"]=> int(1) ["b"]=> int(2) } } object(gfg)#4 (1) { ["value"]=> float(3.14) }
Note: PHP has SplEnum class which can be used for enumerations, though the implementation is not available in all stable versions of PHP.