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--- rfc:null_coercion_consistency [2022/05/05 11:51] – Add note about html templating engines craigfrancis
+++ rfc:null_coercion_consistency [2022/05/11 10:49] – Add round() example craigfrancis
@@ Line 45: / Line 45: @@
   - [[https://www.php.net/manual/en/language.types.boolean.php|To Boolean]]: "When converting to bool, the following values are considered false [...] the special type NULL"
-For example:
+==== Current State ====
 <code php>
@@ Line 116: / Line 116: @@
 ==== Examples ====
-A simple search page:
-<code php>
-$name = $request->get('name');
-if (trim($name) === '') { // Contains non-whitespace characters; so not "", " ", NULL, etc
-  $where_sql[] = 'name LIKE ?';
-  $where_val[] = $name;
-}
-echo '
-  <form action="./" method="get">
-    <label>
-      Search
-      <input type="search" name="name" value="' . htmlspecialchars($name) . '">
-    </label>
-    <input type="submit" value="Go">
-  </form>';
-if ($name !== NULL) {
-  $register_url = '/admin/accounts/add/?name=' . urlencode($name);
-  echo '
-    <p><a href="' . htmlspecialchars($register_url) . '">Add Account</a></p>';
-}
-</code>
-Regarding the source of //$name// (line 1); while frameworks could change their default to an Empty String, or an automated tool could cast the variable to a string, doing so would break the "Add Account" link.
-HTML Templating engines like [[https://github.com/laravel/framework/blob/ab1506091b9f166b312b3990d07b2e21d971f2e6/src/Illuminate/Support/helpers.php#L119|Laravel Blade]] will now suppress this deprecation via null-coalescing ([[https://github.com/laravel/framework/pull/36262/files#diff-15b0a3e2eb2d683222d19dfacc04c616a3db4e3d3b3517e96e196ccbf838f59eR118|patch]]); or [[https://github.com/twigphp/Twig/blob/b4d6723715da57667cca851051eba3786714290d/src/Extension/EscaperExtension.php#L195|Symphony Twig]] will preserve NULL, where it's usually passed to //echo// (despite the [[https://www.php.net/echo|echo documentation]] saying it only accepts non-nullable strings).
-I'd argue a very strict level of type checking (that prevents all forms of coercion) is best done by Static Analysis, which can check if a variable can be nullable, and it can decide if this is a problem, in the same way that a string (e.g. '15') being provided to integer parameter could be seen as a problem.
 Common sources of NULL:
@@ Line 163: / Line 131: @@
 $search = $request->getGet('q'); // CodeIgniter
-$value = array_pop($empty_array);
 $value = mysqli_fetch_row($result);
 $value = json_decode($json); // Invalid JSON, or nesting limit.
+$value = array_pop($empty_array);
 </code>
@@ Line 171: / Line 139: @@
 <code php>
+$rounded_value = round($value);
 $search_trimmed = trim($search);
@@ Line 201: / Line 171: @@
 mail('nobody@example.com', 'subject', 'message', NULL, '-fwebmaster@example.com');
 </code>
+HTML Templating engines like [[https://github.com/laravel/framework/blob/ab1506091b9f166b312b3990d07b2e21d971f2e6/src/Illuminate/Support/helpers.php#L119|Laravel Blade]] suppress this deprecation with null-coalescing ([[https://github.com/laravel/framework/pull/36262/files#diff-15b0a3e2eb2d683222d19dfacc04c616a3db4e3d3b3517e96e196ccbf838f59eR118|patch]]); or [[https://github.com/twigphp/Twig/blob/b4d6723715da57667cca851051eba3786714290d/src/Extension/EscaperExtension.php#L195|Symphony Twig]] which preserves NULL, but it's often passed to //echo// (which accepts it, despite the [[https://www.php.net/echo|echo documentation]] saying it accepts non-nullable strings).
+I'd argue a very strict level of type checking (that prevents all forms of coercion) is best done by Static Analysis, which can check if a variable can be nullable, and it can decide if this is a problem, in the same way that a string (e.g. '15') being provided to integer parameter could be seen as a problem.
 There are approximately [[https://github.com/craigfrancis/php-allow-null-rfc/blob/main/functions-change.md|335 parameters affected by this deprecation]].
@@ Line 343: / Line 317: @@
 ===== Backward Incompatible Changes =====
-None
+While the intention of this RFC is to avoid a BC break; for user defined functions to be updated to also coerce NULL (instead of throwing a Type Error), it's possible some code may rely on that behaviour, for example:
+<code php>
+function my_function(string $my_string) {
+  var_dump($my_string);
+}
+try {
+  my_function('A');   // string(1) "A"
+  my_function(1);     // string(1) "1"
+  my_function(1.2);   // string(3) "1.2"
+  my_function(true);  // string(1) "1"
+  my_function(false); // string(0) ""
+  my_function(NULL);  // Throw Type Error
+} catch (TypeError $e) {
+  // Do something important?
+}
+</code>
 ===== Proposed PHP Version(s) =====
@@ Line 396: / Line 387: @@
 ===== Notes =====
-The **15%** of scripts that do not use //strict_types=1// was calculated using [[https://grep.app/|grep.app]], to "search across a half million git repos", were each result is a script (not a count of matches,  [[https://grep.app/search?q=defuse/php-encryption&filter[lang][0]=PHP|example]]). We can see [[https://grep.app/search?q=strict_types&filter[lang][0]=PHP|272,871]] scripts using //strict_types=1//, out of [[https://grep.app/search?q=php&filter[lang][0]=PHP|1,842,666]]. And keep in mind that [[https://grep.app/search?q=class%20wpdb%20%7B&filter[lang][0]=PHP|WordPress only really appears once]], it is [[https://make.wordpress.org/core/2022/01/10/wordpress-5-9-and-php-8-0-8-1/#php-8-1-deprecation-passing-null-to-non-nullable-php-native-functions-parameters|affected by this deprecation]], and is installed/used by many.
+The **15%** of scripts that use //strict_types=1// was calculated using [[https://grep.app/|grep.app]], to "search across a half million git repos", were each result is a script (not a count of matches,  [[https://grep.app/search?q=defuse/php-encryption&filter[lang][0]=PHP|example]]). We can see [[https://grep.app/search?q=strict_types&filter[lang][0]=PHP|272,871]] scripts using //strict_types=1//, out of [[https://grep.app/search?q=php&filter[lang][0]=PHP|1,842,666]]. And keep in mind that [[https://grep.app/search?q=class%20wpdb%20%7B&filter[lang][0]=PHP|WordPress only really appears once]], it is [[https://make.wordpress.org/core/2022/01/10/wordpress-5-9-and-php-8-0-8-1/#php-8-1-deprecation-passing-null-to-non-nullable-php-native-functions-parameters|affected by this deprecation]], and is installed/used by many.
 In the [[https://wiki.php.net/rfc/scalar_type_hints_v5#behaviour_of_weak_type_checks|Scalar Type Declarations]] RFC for PHP 7.0, scalar types were defined as "int, float, string and bool" - but, despite NULL also being a simple value (i.e. not an array/object/resource), it was not included in this definition. For backwards compatibility reasons this definition is unlikely to change.

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