I want to get the first letter of a string and I've noticed that $str[0] works great. I am just not sure whether this is 'good practice', as that notation is generally used with arrays. This feature doesn't seem to be very well documented so I'm turning to you guys to tell me if it's all right – in all respects – to use this notation?
Or should I just stick to the good ol' substr($str, 0, 1)?
Also, I noted that curly braces ($str{0}) works as well. What's up with that?
Yes. Strings can be seen as character arrays, and the way to access a position of an array is to use the [] operator. Usually there's no problem at all in using $str[0] (and I'm pretty sure is much faster than the substr() method).
There is only one caveat with both methods: they will get the first byte, rather than the first character. This is important if you're using multibyte encodings (such as UTF-8). If you want to support that, use mb_substr(). Arguably, you should always assume multibyte input these days, so this is the best option, but it will be slightly slower.
My only doubt would be how applicable this technique would be on multi-byte strings, but if that's not a consideration, then I suspect you're covered. (If in doubt, mb_substr() seems an obviously safe choice.)
However, from a big picture perspective, I have to wonder how often you need to access the 'n'th character in a string for this to be a key consideration.
Speaking as a mere mortal, I would stick with $str[0]. As far as I'm concerned, it's quicker to grasp the meaning of $str[0] at a glance than substr($str, 0, 1). This probably boils down to a matter of preference.
As far as performance goes, well, profile profile profile. :) Or you could peer into the PHP source code...
I've used that notation before as well, with no ill side effects and no misunderstandings. It makes sense -- a string is just an array of characters, after all.
