What does the $ var & 1 syntax in array_filter mean?

& Amp; yes. what does one mean? it doesn't seem to be a reference transfer. then, the result is 3. I don't know much about it. who can give me two sentences, thank you {code ...} & yes. what does it mean? it doesn't seem to be a reference transfer. then the result is 3. I don't know much about it. who can give me two sentences? thank you.

  Print result Array ([3] => 3)

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& Yes. what does it mean? it doesn't seem to be a reference transfer. then the result is 3. I don't know much about it. who can give me two sentences? thank you.

  Print result Array ([3] => 3)

Php bitwise operator-bitwise AND, test_odd is a function that determines an odd number.

However, some important words in this section are in English:

If&,|,^Both operands of are strings, which first converts the strings into the corresponding ascii code and then bitwise operations. In other cases, convert them into integers before bitwise operations.

So althoughAThe ascii code is 97, but it will still be filtered out.