What does {0} mean in a PHP statement?

Apols if this has been asked before. I am using someone else's PHP code and 开发者_JS百科came across the following line:

if($_GET['file']{0}=='.') die('Wrong file!');

The if, $_GET and die I understand, but what is the meaning of the {0} after the $_GET['file']? I've looked through a number of tutorials and didn't come across the answer.

TIA.

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$str{0} will return the first character/byte of a string. But the syntax $str{0} is deprecated in favor of $str[0]:

Note: Strings may also be accessed using braces, as in $str{42}, for the same purpose. However, this syntax is deprecated as of PHP 5.3.0. Use square brackets instead, such as $str[42].

If you’re working with multi-byte characters, use mb_substr instead.

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The {0} is the same as [0]. So, $_GET['file']{0} is getting the zeroth character from $_GET['files'].

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It's shorthand for accessing the first character of the string. $_GET['file']{1} would be the second character, and so on. So in your example it's checking to see whether the first character is a dot, and if so, exiting; presumably to avoid people passing paths in the URL such as ../../../etc/passwd.

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As others have said, it's looking at string position 0 in the variable $_GET['file'] and throwing an error if that happens to be a dot.

This looks like a (relatively crude) way of preventing hack attacks by blocking the user if he tries to access a file that starts with a dot.