Why is this search form not submitting when button is clicked?

I suggest you use <input type="submit" /> or <button type="submit" />.

<input type="button" /> is valid but doesn’t submit the form by default (without you adding any ajax/js magic to it.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)