Random item from a repeater and max amount based on item count

Hi Guys,

I have a template that has a repeater to upload an image. I want to choose only one of these images at random and display it. I have this working with the following code.

Template

~~ <perch:repeater id="images" label="Images" scope-parent="true"> <perch:if id="perch_item_index" match="eq" value="{landimg}" /> <img src="<perch:content id="image" type="image" width="1400" label="Image" help="Recommended that images must be at least 1400px wide and that you use square images" bucket="images" />"

                    srcset="
                    <perch:content id="image" type="image" width="1400" /> <perch:content id="image" type="image" width="1400" output="w" />w,
                    <perch:content id="image" type="image" width="1200" /> <perch:content id="image" type="image" width="1200" output="w" />w,
                    <perch:content id="image" type="image" width="800" /> <perch:content id="image" type="image" width="800" output="w" />w,
                    <perch:content id="image" type="image" width="600" /> <perch:content id="image" type="image" width="600" output="w" />w,
                    <perch:content id="image" type="image" width="350" /> <perch:content id="image" type="image" width="350" output="w" />w,
                "

                sizes="
                    (min-width: 68.750em) 33vw,
                    (min-width: 47.500em) 50vw,
                    100vw
                "

                alt="<perch:content id="parent.heading" />"

                class="section-teaser__image"
            >

</perch:if> </perch:repeater>

        <div class="section-teaser__content">
            <h2 class="section-teaser__title"><perch:content id="heading" type="smarttext" label="Heading" required="true" title="true" /></h2>
            <span class="section-teaser__subline"><perch:content id="subline" type="smarttext" label="Subline" required="true" title="true" />&hellip;</span>
            <p class="section-teaser__readmore">View Our Range</p>
        </div>

and PHP page

    <?php
        PerchSystem::set_var('landimg', rand(1, 2));
        perch_content_custom('Product Box  - Land', array(
            'template'=>'home/product_box.html'
        ));
    ?>

~~~

However, as there will be several of these boxes and each item might contain a varying amount of images I would like to check how many items each repeater has and then set this as the top amount as to not produce a random number that an image doesn't exist.

So my question is how can I check how many items are in the repeater and then change this to set the maximum value? PerchSystem::set_var('landimg', rand(1, MAXVLAUE));

I tried to use <perch:content id="perch_item_count" hidden="true" /> but I think this is only accessible inside the template and not outside so I cannot use it in my PHP code?

Any suggestions?

Thanks.