First to say that the PHP variable naming rules, Baidu next catch a lot: (1) PHP variable name is case-sensitive; (2) The variable name must begin with the dollar sign $; (3) The beginning of the variable name can be underlined; (4) The variable name cannot begin with a numeric character. In fact, all programming is similar to the naming convention is: 1. The first character of a variable is preferably a letter or _ and cannot begin with a number 2. The second character begins to allow numbers, letters, _ Well, that's pretty much it, but that's not the point. Today we talk about the available characters for PHP variables, not just numbers, letters, _ Oh. A few days ago QQ A friend sent me a shell, is encrypted, all garbled, but there are comments, called "God Shield Encryption" good domineering appearance. It uses some of the more obscure points of knowledge, the most obvious is the variable name, so today we start from the variable to speak. Of course I didn't find authoritative material. Powerful description of PHP variable name available character information, so I can only test it myself. (English is not good, no way Google to the good evidence) first look at the method I used, if you have a better way, want to share. ) <?php if ($_post) { $CHR = chr ($_post[' CHR ']) eval (' $ '. $chr. = 1; "); echo ' OK '; exit; ?> <!doctype html>
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