Let's talk about php7 XOR error situations

PHP7's XOR operator may cause errors in some cases. This article will introduce you to the use of the XOR operator and the situations that may cause errors.

First, let us understand the XOR operator (^) in PHP. The XOR operator returns a result in which only one of the two operands is true. For example, 1^0 returns 1 because one of the operands is true. 1^1 will return 0 because both operands are true.

Before PHP7, the XOR operator behaved as bitwise XOR for two string operands, while in PHP7, it is considered invalid for string operands and returns FALSE.

However, in some cases, the XOR operator may cause unexpected results due to PHP's weak typing.

For example, consider the following code:

$a = "1 and 2";
$b = "0b10";

if ($a ^ $b) {
    echo "TRUE";
} else {
    echo "FALSE";
}

In this example, $a is a string "1 and 2" and $b is a string "0b10", which is interpreted as A binary number 2. In this case, the XOR operator converts the operands into numbers and then performs a bitwise XOR operation. Therefore, this code snippet will output "TRUE" instead of "FALSE" because the result of 1^2 is 3 and this conditional expression will be treated as TRUE.

Similarly, strange errors may occur when processing contains NULL values. For example:

$a = "hello";
$b = NULL;

if ($a ^ $b) {
    echo "TRUE";
} else {
    echo "FALSE";
}

In this example, $b is a NULL value, so the code snippet will output "TRUE" because "hello" will be converted to 0, and the result of 0 ^ NULL is still 0.

To avoid these errors, explicit type conversions should always be used. For example, to explicitly convert string operands to integers:

$a = "1 and 2";
$b = "0b10";

if ((int)$a ^ (int)$b) {
    echo "TRUE";
} else {
    echo "FALSE";
}

In this example, we convert $a and $b to integers and then XOR them together. This will ensure that only two integers are bitwise XORed.

In summary, PHP7's XOR operator may cause unexpected results because it converts a string to a number and performs a bitwise XOR operation. To avoid these errors, you should use explicit type conversions.

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