Irony Porphyria's Lover

In Robert Browning's poem "Porphyria's Lover" irony is a common theme. This is rather apparent as soon as the reader knows that the speaker has killed Porphyria. The reader does not know this, though, until after the speaker has given a detailed account of how much he loves Porphyria and her beauty. The scene is set up perfectly for a romantic engagement, wherein Porphyria has offered the speaker her bare shoulder. The speaker is so overwheled with how pristine the moment is, that he doesn't know what to do. This is where the irony comes in. Though the speaker is so in love with Porphyria, he kills her to capture the beauty of the affair.
This is the main theme of the poem, but it is not the sole sample of irony. At one point in the speaker's description of Porphyria, he is taken by her hair's gorgeousness. In the end of the story, he finally uses her hair to strangle her. This is obviously ironic.
The irony of Browning's poem is what brings the whole story together. Without it, we'd be left to think that the speaker is a senseless killer with some creepy tendencies.