search form with category selection

[slave]

I would like to create a search form with a category selection.
I do not get the selector, I need help

my selector

$katId = $pages->find("template=leftnav_kat, h1_h6_1%=$kat"); its ok
$matches = $pages->find("template=site, has_parent=$katId"); its ok
myresult this pages (templates = site):

MedLab ML +2 °C bis +8 °C 41 Liter
MedLab ML +2 °C bis +8 °C 41 Liter
MedLab ML +2 °C bis +8 °C 45 Liter
MedLab ML +2 °C bis +8 °C 82 Liter
MedLab ML +2 °C bis +8 °C 82 Liter
LabStar Sanguis +2 °C bis +6 °C 100 Liter
MedLab ML +2 °C bis +8 °C 107 Liter
LabStar Sanguis +2 °C bis +6 °C 100 Liter
MedLab ML +2 °C bis +8 °C 82 Liter

but I'm looking for a text in the template = site, this template has a field search_cache

$katId = $pages->find("template=leftnav_kat, h1_h6_1%=$kat"); its ok
$matches = $pages->find("template=site, has_parent=$katId, search_cache%=Industrie"); not work

I need help