0' as a String with Empty() in PHP

0' as a string with empty() in PHP

You cannot make empty() take it. That is how it was designed. Instead you can write an and statement to test:

if (empty($var) && $var !== '0') {
    echo $var . ' is empty';
}

You could use isset, unless of course, you want it to turn away the other empties that empty checks for.

How to convert empty string to zero?

The only real way is to typecast:

<?php
    $str = '';
    echo (int)$str;

However, if this is dynamically assigned then you'll have to use an if statement. But fear not, ternary exists:

echo (empty($str) ? 0 : $str);

With the thanks of Dharman, we can Elvis it up a bit:

echo $str ?: 0;

Though, note that if $str is not defined PHP will throw a undefined notice. For that reason either stick to ternary or ensure the variable is declared before usage.

In php, is 0 treated as empty?

http://php.net/empty

The following things are considered to be empty:

"" (an empty string)

0 (0 as an integer)

0.0 (0 as a float)

"0" (0 as a string)

NULL

FALSE

array() (an empty array)

var $var; (a variable declared, but without a value in a class)

Note that this is exactly the same list as for a coercion to Boolean false. empty is simply !isset($var) || !$var. Try isset instead.

empty() returns true if a zero float value was passed as string

This zero/empty condition works the same way in both PHP 7 and 8 versions:

if (empty($var) || (is_numeric($var) && (float)$var == 0))

It checks if $var is any of the following:
not set, null, (bool)false, (int)0, (float)0.00, (string)"", (string)"0", (string)"0.00", or (array)[]

And to substitute empty():

  // Checks if variable is not set, null, (bool)false, (int)0, (float)0.00, (string)"", (string)"0", (string)"0.00", (array)[], or array with nil nodes
function nil(&$var) { // https://www.dictionary.com/browse/nil
  return (empty($var) || (is_numeric($var) && (float)$var == 0));
}

To be used like:

if (nil($var)) {
  echo 'The value is either not set, an empty string, empty array, null, or equals zero.';
}

It can be expanded to check subnodes for arrays as well:

  // Checks if variable is not set, null, (bool)false, (int)0, (float)0.00, (string)"", (string)"0", (string)"0.00", (array)[], or array with nil nodes
  function nil(&$var) {
    if (is_array($var)) {
      foreach ($var as $node) {
        if (!nil($node)) return !1;
      }
    }
    return (empty($var) || (is_numeric($var) && (float)$var == 0));
  }

Empty string comparison to zero gives different result in PHP 8 than in previous versions

You are right, this is a major change.

As with any version upgrade, you can find a guide to Migrating to PHP 8.0 in the official PHP manual. If you click on Backward Incompatible Changes you will see that this change is the very first thing on that page:

Non-strict comparisons between numbers and non-numeric strings now work by casting the number to string and comparing the strings.

As well as an example in the next sentence, there is a before-and-after comparison table which includes the exact example you gave:

Comparison: 0 == ""; Before: true; After: false

If you have code that was relying on the old behaviour, you will need to update it to be more explicit about the values expected. For instance, all of the following work in all versions of PHP:

if ( $value === 0 || $value === "" ) { ... }
if ( (string)$zero === "" ) { ... }
if ( (int)$emptyString === 0 ) { ... }

For more background on the change, you can read the original proposal here: PHP RFC: Saner string to number comparisons

PHP: what's an alternative to empty(), where string 0 is not treated as empty?

The answer to this is that it isn't possible to shorten what I already have.

Suppressing notices or warnings is not something I want to have to do, so I will always need to check if empty() or isset() before checking the value, and you can't check if something is empty() or isset() within a function.

PHP: using empty() for empty string?

You should not use empty (or isset) if you expect $foo to exist. That means, if according to your program logic, $foo should exist at this point:

if ($foo === '')

Then do not do any of these:

if (isset($foo))
if (empty($foo))

These two language constructs suppress error reporting for undefined variables. That's their only job. That means, if you use isset or empty gratuitously, PHP won't tell you about problems in your code. For example:

$foo = $bar;
if (empty($føø)) ...

Hmm, why is this always true, even when $bar contains the expected value? Because you mistyped the variable name and you're checking the value of an undefined variable. Write it like this instead to let PHP help you:

if (!$føø) ...

Notice: undefined variable føø on line ...

The condition itself is the same, == false (!) and empty produce the same outcome for the same values.

How exactly to check for an empty string depends on what values you do or don't accept. Perhaps $foo === '' or strlen($foo) == 0 is the check you're looking for to ensure you have a string with something in it.

float 0 returns as empty string in php

This is because in PHP the following expressions are true:

0 == ""
0.0 == ""

not because $empty here is the empty string "".

You can perform a typed equality check using ===, and these expressions will appear false, as expected:

0 === ""
0.0 === ""

0' as a String with Empty() in PHP