ReflectionParameter::isCallable

Returns whether parameter MUST be callable

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See the example below for an alternative way to derive this information.

&reftitle.description; public `bool` `ReflectionParameter::isCallable`

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Returns &true; if the parameter is `callable`, &false; if it is not or &null; on failure.

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### PHP 8.0.0 equivalent

As of PHP 8.0.0, the following code will report if a type supports callables, including as part of a union.

    <?php
    function declaresCallable(ReflectionParameter $reflectionParameter): bool
    {
        $reflectionType = $reflectionParameter->getType();

        if (!$reflectionType) return false;

        $types = $reflectionType instanceof ReflectionUnionType
            ? $reflectionType->getTypes()
            : [$reflectionType];

       return in_array('callable', array_map(fn(ReflectionNamedType $t) => $t->getName(), $types));
    }
    ?>