Add function createTextSnippet() for shortening text to an expected

length

Close #1

MD_STD.php

@@ -356,4 +356,26 @@ final class MD_STD {
 
     }
 
+    /**
+     * This function cuts down a string and adds a period in case it's longer
+     * than length to create a snippet.
+     *
+     * @param string  $string Input text to cut down.
+     * @param integer $length Length of the snippet to create.
+     *
+     * @return string
+     */
+    public static function createTextSnippet(string $string, int $length = 180):string {
+
+        if (\mb_strlen($string) > $length) {
+            $string  = \mb_substr($string, 0, $length);
+            if (($lastWhitespace = \mb_strrpos($string, ' ')) !== false) {
+                $string = \mb_substr($string, 0, $lastWhitespace);
+            }
+            $string .= '...';
+        }
+        return $string;
+
+    }
+
 }