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Bitwise OR operator in PHP, Bug or Feature?

echo 'https://www.tehplayground.com/' | '/';

Results in 'ottps://www.tehplayground.com/'

Why?

Solution

  • That's due to the bitwise OR operator. It interprets each string as binary and performs the operation.

    01101000 // 'h'
00101111 // '/'
-- OR --
01101111 // 'o'

    ^ looking at the first character

    Further Explanation

    PHP seems to loop through each character of a string and apply the bitwise operator to it.

    So what actually happens is more like:

    "h" | "/" -> "o"
"t" | "" -> "t"
"t" | "" -> "t"
"p" | "" -> "p"
...

    Any empty string in bitwise operations would end up being all 0s in binary, so if we just look at the first two characters for comparison

    // character at index [0]
"h" -> 01101000 (104)
"/" -> 00101111 (47)
-- OR --
"o" -> 01101111 (111)

// character at index [1]
"t" -> 01110100 (116)
""  -> 00000000 (0)
-- OR --
"t" -> 01110100 (116)