php - count() emitting an E_WARNING

Question

Prior to PHP 7.2 using count() on a scalar value or non-countable object would return 1 or 0.

For example: https://3v4l.org/tGRDE

var_dump(count(123)); //int(1)
var_dump(count(new stdclass)); //int(1)
var_dump(count('hello world'));  //int(1)
var_dump(count(null));  //int(0)

In the updates to PHP 7.2+, using count() as demonstrated above will emit a warning message.

An E_WARNING will now be emitted when attempting to count() non-countable types (this includes the sizeof() alias function).

Warning: count(): Parameter must be an array or an object that implements Countable [sic]

As a result many popular Frameworks will elevate the E_WARNING and throw an Exception instead.

[ErrorException] count(): Parameter must be an array or an object that implements Countable

The error elevation behavior was also commented on by the PHP developers.

Environments that display warnings or convert them to more severe errors/exceptions would be affected, but this should just bring attention to a bug in the code.

How can the previous behavior of count() be achieved in PHP 7.2+, that does not emit an E_WARNING, without modifying the error reporting setting and without using @count()?

Answer 1

As we discussed, there are multiple ways to achieve the original functionality of count() and not emit an E_WARNING.

In PHP 7.3 a new function was added is_countable, specifically to address the E_WARNING issue and the prevalence of applications adopting is_array($var) || $var instanceof Countable in their code.

In PHP 7.2, a Warning was added while trying to count uncountable things. After that, everyone was forced to search and change their code, to avoid it. Usually, the following piece of code became standard:

if (is_array($foo) || $foo instanceof Countable) { // $foo is countable }

https://wiki.php.net/rfc/is-countable

---

Custom Function Replacement

For that reason it seems the best method of resolving the issue, is to perform the same functionality that PHP is doing with is_countable and creating a custom function to ensure compliance with the original functionality of count.

Example https://3v4l.org/8M0Wd

function countValid($array_or_countable, $mode = COUNT_NORMAL)
{
    if (
        (PHP_VERSION_ID >= 70300 && is_countable($array_or_countable)) ||
        is_array($array_or_countable) ||
        $array_or_countable instanceof Countable
    ) {
        return count($array_or_countable, $mode);
    }

    return null === $array_or_countable ? 0 : 1;
}

Result

array: 3
string: 1
number: 1
iterator: 3
countable: 3
zero: 1
string_zero: 1
object: 1
stdClass: 1
null: 0
empty: 1
boolt: 1
boolf: 1

Notice: Undefined variable: undefined in /in/8M0Wd on line 53
undefined: 0

---

Shim is_countable() function

Using the above replacement function, it is also possible to shim is_countable in PHP <= 7.2, so it is only used when needed, with minimal overhead.

Example https://3v4l.org/i5KWH

if (!function_exists('is_countable')) {
    function is_countable($value)
    {
        return is_array($value) || $value instanceof Countable;
    }
}

function countValid($array_or_countable, $mode = COUNT_NORMAL)
{
    if (is_countable($array_or_countable)) {
        return count($array_or_countable, $mode);
    }

    return null === $array_or_countable ? 0 : 1;
}

---

Ignore count() Warnings

As the functionality of count() has not changed and not did not typically emit warnings in the past. An alternative to using a custom function, is to ignore the warning outright by using the @ Error Control Operator

Warning: This approach has the impact of treating undefined variables as NULL and not displaying Notice: Undefined variable: message.

Example https://3v4l.org/nmWmE

@count($var);

Result

array: 3
string: 1
number: 1
iterator: 3
countable: 3
zero: 1
string_zero: 1
object: 1
stdClass: 1
null: 0
empty: 1
boolt: 1
boolf: 1
---
Undefined: 0

---

Replace count() using APD extension

As for replacing the internal PHP function count(). There is a PECL extension APD (Advanced PHP Debugger), that allows for override_function that works on core PHP functions. As the extension name suggests, it is technically meant for debugging, but is a viable alternative to replacing all instances of count for a custom function.

Example

ename_function('count', 'old_count');
override_function('count', '$array_or_countable,$mode', 'return countValid($array_or_countable,$mode);');

if (!function_exists('is_countable')) {
    function is_countable($value)
    {
        return is_array($value) || $value instanceof Countable;
    }
}

function countValid($array_or_countable, $mode = COUNT_NORMAL)
{
    if (is_countable($array_or_countable)) {
        return old_count($array_or_countable, $mode);
    }

    return null === $array_or_countable ? 0 : 1;
}