Add type-safe wrapper around preg_replace for replacing in strings

MD_STD.php

@@ -115,6 +115,26 @@ class MD_STD {
 
     }
 
+    /**
+     * Type-safe(r) wrapper around preg_replace.
+     *
+     * @param string $pattern     The pattern to search for. It can be either a string or an array with strings.
+     * @param string $replacement To replace with.
+     * @param string $subject     The string or an array with strings to search and replace.
+     *
+     * @return string
+     */
+    public static function preg_replace_str(string $pattern, string $replacement, string $subject):string {
+
+        $output = preg_replace($pattern, $replacement, $subject);
+        if ($output === null) {
+            throw new Exception("Error replacing in $subject: Replacing $pattern with $replacement");
+        }
+
+        return $output;
+
+    }
+
     /**
      * Type-safe wrapper around json_encode.
      *