Check if a class constant exists
How can I check if a constant is defined in a PHP class?
class Foo {
const BAR = 1;
}
Is there something like property_exists()
or method_exists()
for class constants? Or can I just use defined("Foo::BAR")
?
You can check if a constant is defined with the code below:
<?php
if(defined('className::CONSTANT_NAME')){
//defined
}else{
//not defined
}
Yes, just use the class name in front of the constant name:
defined('SomeNamespace\SomeClass::CHECKED_CONSTANT');
http://www.php.net/manual/en/function.defined.php#106287
You have 3 ways to do it:
defined()
[PHP >= 4 - most retro-compatible way]
$class_name = get_class($object); // remember to provide a fully-qualified class name
$constant = "$class_name::CONSTANT_NAME";
$constant_value = defined($constant) ? $constant : null;
Note: using defined()
on a private constant (possible from PHP7.1) will throw error: "Cannot access private const". While using ReflectionClass
or ReflectionClassConstant
will work.
ReflectionClass
[PHP >= 5]
$class_reflex = new \ReflectionClass($object);
$class_constants = $class_reflex->getConstants();
if (array_key_exists('CONSTANT_NAME', $class_constants)) {
$constant_value = $class_constants['CONSTANT_NAME'];
} else {
$constant_value = null;
}
ReflectionClassConstant
[PHP >= 7.1.0]
$class_name = get_class($object); // fully-qualified class name
try {
$constant_reflex = new \ReflectionClassConstant($class_name, 'CONSTANT_NAME');
$constant_value = $constant_reflex->getValue();
} catch (\ReflectionException $e) {
$constant_value = null;
}
There is no real better way. Depends on your needs and use case.