If anybody else wanted to show a success message with inertia using flash, it was a bit complicated to find so thought I'd share here;

In Middleware, HandleInertiaRequest

  public function share(Request $request): array
    {
        return [
            ...parent::share($request),
            'ziggy' => fn () => [
                ...(new Ziggy)->toArray(),
                'location' => $request->url(),
            ],
            'flash' => [
                'success' => $request->session()->get('success'),
                'error' => $request->session()->get('error'),
            ],
        ];
    }

In controller

        return redirect()->back()->with('success', 'Comment added successfully');

And in your component add

<div v-if="$page.props.flash.success">
        <FlashMessage :success="$page.props.flash.success"/>
    </div>
    <div v-if="$page.props.flash.error">
        <FlashMessage :error="$page.props.flash.error"/>
    </div>

FlashMessage Component

<script setup>
import { defineProps, ref, onMounted } from 'vue';

defineProps({
    success: {
        type: String,
        required: false,
    },
    error: {
        type: String,
        required: false,
    },
});

const showMessage = ref(false);

onMounted(() => {
        showMessage.value = true;
        setTimeout(() => {
            showMessage.value = false;
        }, 6000);
});


</script>

<template>
    <div v-if="success && showMessage">
        <div class="absolute top-6 right-8 h-18 w-30 bg-green-100 bg-opacity-40 border-l-4 border-green-500 text-green-700 p-4 rounded-lg">
            <p class="text-lg font-semibold">Success</p>
            <p>{{ success }}</p>
        </div>
    </div>
    <div v-if="error && showMessage">
        <div class="absolute top-6 right-8 h-18 w-30 bg-red-100 bg-opacity-40 border-l-4 border-red-500 text-red-700 p-4 rounded-lg">
            <p class="text-lg font-semibold">Error</p>
            <p>{{ error }}</p>
        </div>
    </div>
</template>

Always Validate. Never Trust the User.

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