Db: add count() helper method

src/Db.php

@@ -196,6 +196,34 @@ class Db {
     return false;
   }
 
+  /**
+   * Helper to retreive a count from a table of the database
+   * @param string $table               The table name
+   * @param array|string $where         WHERE clause(s) as expected by Envms\FluentPDO\Query
+   * @param array|string|null $what     What to count (optional, default: "*")
+   * @param array<array{0: 'LEFT'|'RIGHT'|'INNER'|'OUTER'|'FULL', 1: string, 2: string}>|array{0: 'LEFT'|'RIGHT'|'INNER'|'OUTER'|'FULL', 1: string, 2: string} $joins    Join specification as array (see apply_joins())
+   * @return array|false
+   */
+  public function count($table, $where, $what=null, $joins=null) {
+    try {
+      $query = $this -> fpdo -> from($table) -> where($where);
+      if ($joins)
+        self :: apply_joins($query, $joins);
+      $query -> select(null) -> select(sprintf("COUNT(%s) as count", $what?$what:"*"));
+      if ($query->execute() === false)
+        return false;
+      $return = $query->fetchAll();
+      if (is_array($return) && count($return) == 1)
+        return $return[0]["count"];
+    }
+    catch (Exception $e) {
+      self :: _log_simple_select_query_error(
+        false, $table, $e, $where, null, null, null, $joins
+      );
+    }
+    return false;
+  }
+
   /**
    * Mapping of JOIN type with corresponding query object method
    * @var array<string,string>