$aa[bar] will report an error, right? PHP will consider bar as a constant
If you don’t add single quotes, there will be no error, and the results will be output as usual, but there will be a warning to remind you to add single quotes
Variables with $
Strings with quotes
That’s either an array, a constant or a built-in function, right?
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If you don’t add single quotes, there will be no error, and the results will be output as usual, but there will be a warning to remind you to add single quotes
Variables with $
Strings with quotes
That’s either an array, a constant or a built-in function, right?