title: List of functions disallowing passing null to parameter
body: <p>I am starting my upgrades to PHP 8.1, and one of the issues that I'm running into is the <em>Passing null to parameter #1 ($string) of type string is deprecated</em>.  (see <a href="https://stackoverflow.com/questions/70574048/passing-null-to-non-nullable-internal-function-parameters-updating-existing-co">related question</a> and the <a href="https://wiki.php.net/rfc/deprecate_null_to_scalar_internal_arg" rel="nofollow noreferrer">problematic RFC</a>)</p>
  <p>For example, by default all my database results are run through <code>htmlspecialchars()</code>, which will lead to a problem if that field is <code>null</code>, as illustrated here:</p>
  <pre><code>php &gt; $foo = null;
  php &gt; echo htmlspecialchars($foo);
  PHP Deprecated:  htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated in php shell code on line 1
  
  Deprecated: htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated in php shell code on line 1
  php &gt;  
  </code></pre>
  <p>Since legacy code relied on duck typing, this could crop up <em>anywhere</em>, with who-knows-how-many functions. I will have to manually search through all the legacy code to find the instances where a <code>null</code> <em><strong>MIGHT</strong></em> be evaluated.</p>
  <p>So far, I have not been able to find a list of the internal functions that have been <s>broken</s> fixed. Can anybody point me to a list of these functions?</p>