Print name or definition of callable in PHP - php

Question

Callables in PHP can be in a lot of forms, like an object, an array, or a string containing a function name.
If I got a callable like this in a variable how can I print some user friendly "definition" of it in the log.
Think of this code:
call_user_func($callable);
$logger->log("Provided callable " . (string) $callable . " called");
Problem is, this raises error, for example array to string conversion error. What is the best way to print out something useful about that callable?

Answer 1

Very old question but since i just used this to log some info, i thought it could use some clarification.
The comment by #Fabian Picone is a bit misleading.
The type hint actually works with string (arrays too), but the string MUST be an existing method or function (if you add function foo() {} in your code it will work). And that is, it must actually be callable. The error message is not that intuitive.
See this answer too https://stackoverflow.com/a/63289789/7409925.
This is my take that i'm using for logging (expanded from #Seb's), adding support for invokables and removing unnecessary trim's:
function getCallableName(callable $callable) {
switch (true) {
case is_string($callable) && strpos($callable, '::'):
return '[static] ' . $callable;
case is_string($callable):
return '[function] ' . $callable;
case is_array($callable) && is_object($callable[0]):
return '[method] ' . get_class($callable[0]) . '->' . $callable[1];
case is_array($callable):
return '[static] ' . $callable[0] . '::' . $callable[1];
case $callable instanceof Closure:
return '[closure]';
case is_object($callable):
return '[invokable] ' . get_class($callable);
default:
return '[unknown]';
}
}

Answer 2

Something like this should work:
function getCallableName($callable) {
if (is_string($callable)) {
return trim($callable);
} else if (is_array($callable)) {
if (is_object($callable[0])) {
return sprintf("%s::%s", get_class($callable[0]), trim($callable[1]));
} else {
return sprintf("%s::%s", trim($callable[0]), trim($callable[1]));
}
} else if ($callable instanceof Closure) {
return 'closure';
} else {
return 'unknown';
}
}

Answer 3

Inspired by an answer of #Bigdot https://stackoverflow.com/a/68113840/6916271 I created 2 methods, which could be useful when we need to retrieve the context of callable.
I used result together with Monolog, but it is also possible to use it with print_r(), json_encode(), var_dump() or var_export() if you need to convert it to string.
The main difference here compared to the answer above is extended information about closure, which might be needed during an investigation.
/**
* Retrieve the context of callable for debugging purposes
*
* #param callable $callable
* #return array
*/
private function getCallableContext(callable $callable): array
{
switch (true) {
case \is_string($callable) && \strpos($callable, '::'):
return ['static method' => $callable];
case \is_string($callable):
return ['function' => $callable];
case \is_array($callable) && \is_object($callable[0]):
return ['class' => \get_class($callable[0]), 'method' => $callable[1]];
case \is_array($callable):
return ['class' => $callable[0], 'static method' => $callable[1]];
case $callable instanceof \Closure:
try {
$reflectedFunction = new \ReflectionFunction($callable);
$closureClass = $reflectedFunction->getClosureScopeClass();
$closureThis = $reflectedFunction->getClosureThis();
} catch (\ReflectionException $e) {
return ['closure' => 'closure'];
}
return [
'closure this' => $closureThis ? \get_class($closureThis) : $reflectedFunction->name,
'closure scope' => $closureClass ? $closureClass->getName() : $reflectedFunction->name,
'static variables' => $this->formatVariablesArray($reflectedFunction->getStaticVariables()),
];
case \is_object($callable):
return ['invokable' => \get_class($callable)];
default:
return ['unknown' => 'unknown'];
}
}
/**
* Format variables array for debugging purposes in order to avoid huge objects dumping
*
* #param array $data
* #return array
*/
private function formatVariablesArray(array $data): array
{
foreach ($data as $key => $value) {
if (\is_object($value)) {
$data[$key] = \get_class($value);
} elseif (\is_array($value)) {
$data[$key] = $this->formatVariablesArray($value);
}
}
return $data;
}
In we use logger
try {
\call_user_func($callable);
} catch (\Throwable $e) {
$logger->log(
'Error occurred',
['exception' => $e, 'callable' => $this->getCallableContext($callable)]
);
//In case we can use string only
$logger->log('Error occurred: ' . \print_r($this->getCallableContext($callable), true));
}