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 = "neveropen"; 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); ?> |
Output:
string(13) "neveropen"
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 = "neveropen"; 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); ?> |
Output:
object(gfg)#1 (1) {
["value"]=>
string(13) "neveropen"
}
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 = "neveropen"; 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); ?> |
Output:
IllegalArgumentExceptionobject(gfg)#1 (1) {
["value"]=>
string(13) "neveropen"
}
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.
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