I've noticed many (all?) PHP constants have a single-letter prefix, like E_NOTICE, T_STRING, etc. When defining a set of class constants that work in conjunction with one another, do you prefer to follow similar practice, or do you prefer to be more verbose?

class Foo {
    // let's say 'I' means "input" or some other relevant word
    const I_STRING = 'string';
    const I_INTEGER = 'integer';
    const I_FLOAT = 'float';
}

or

class Bar {
    const INPUT_STRING = 'string';
    const INPUT_INTEGER = 'integer';
    const INPUT_FLOAT = 'float';
}