Can't bind past texture unit 7 in OpenGL ES for iOS?

glActiveTexture(GL_TEXTURE8) results in GL_INVALID_ENUM. Shouldn’t I have access to 32 texture units on the iPhone?

OpenGL ES 2.0 only guarantees 8 texture units. Specific implementations may provide more; you can check the value using glGetIntegerv(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS).