Symbol is a special primitive data type, indicating an unique identifier.
This symbol library implementation is similar to alternative types in:
- Symbols in JavaScript: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol
- Symbols in Ruby: https://ruby-doc.org/core-2.5.0/Symbol.html
- Symbols in TypeScript: https://www.typescriptlang.org/docs/handbook/symbols.html
- Atoms in Erlang: http://erlang.org/doc/reference_manual/data_types.html#atom
- ...e.g.
In order to create a new symbol data type, you should use
the Symbol::create() method or call the global symbol()
helper function.
<?php
$a = symbol();
// OR
$b = \Serafim\Symbol\Symbol::create();Each symbol can have a name (description), which is passed as the first parameter.
<?php
$symbol = symbol('id');Please note that the symbols are unique regardless of the names.
<?php
var_dump(symbol() === symbol());
// expected output: false
var_dump(symbol('example') === symbol('example'));
// expected output: falseSymbols can be used as variable values and even constant!
<?php
define('EXAMPLE', symbol());
var_dump(is_symbol(EXAMPLE));
// expected output: true
class Example
{
public const CLASS_CONST = EXAMPLE;
}
var_dump(is_symbol(Example::CLASS_CONST));
// expected output: trueHowever cannot be serialized:
<?php
serialize(symbol());
// ErrorNotice that the symbols are neither a string, nor a number, nor anything (almost :3) else.
<?php
var_dump(\is_string(symbol()));
// expected output: false
var_dump(\is_int(symbol()));
// expected output: false
var_dump(\is_float(symbol()));
// expected output: false
var_dump(\is_bool(symbol()));
// expected output: false
var_dump(\is_array(symbol()));
// expected output: false
var_dump(\is_object(symbol()));
// expected output: false
var_dump(\is_null(symbol()));
// expected output: false
var_dump(\is_symbol(symbol()));
// expected output: true
var_dump(\is_resource(symbol()));
// expected output: trueNote that symbols are always passed by reference and cloning not allowed.
<?php
$a = symbol();
$b = $a;
var_dump($a === $b);
// expected output: true
var_dump(clone $a);
// ErrorAnd in order to get the name of a symbol,
just use the Symbol::key() method:
<?php
use Serafim\Symbol\Symbol;
var_dump(Symbol::key(symbol('hello')));
// expected output: "hello"
var_dump(Symbol::key(symbol('hello')) === Symbol::key(symbol('hello')));
// expected output: true
var_dump(symbol('hello') === symbol('hello'));
// expected output: falseAnd you can find out some details about this type:
<?php
use Serafim\Symbol\Symbol;
$reflection = Symbol::getReflection(Symbol::create('hello'));
$reflection->getName(); // Contains "hello" string
$reflection->getFileName(); // Provides path/to/file-with-symbol-definition.php
$reflection->getStartLine(); // Provides definition line
// etc...
In addition to all this, you can use the Symbol::for method to create
a global symbol. The Symbol::for($key) method searches for existing symbols
in a runtime-wide symbol registry with the given key and returns it if
found. Otherwise a new symbol gets created in the global symbol registry
with this key.
<?php
use Serafim\Symbol\Symbol;
var_dump(Symbol::for('a') === Symbol::for('a'));
// expected output: true
var_dump(Symbol::create('a') === Symbol::for('a'));
// expected output: falseAnd method Symbol::keyFor($symbol) returns a name
for a global symbol.
<?php
var_dump(Symbol::keyFor(Symbol::for('a')));
// expected output: "a"
var_dump(Symbol::keyFor(Symbol::create('a')));
// expected output: null
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent