Which of the following is not a valid way to increment a variable in PHP?$var++;++$var;$var += 1;$var =+ 1

To determine which of the provided options is not a valid way to increment a variable in PHP, let's analyze each option:

1. **$var++**: This is a valid way to increment the variable. It increases the value of `$var` by 1 after the statement is executed.

2. **++$var**: This is also a valid way to increment the variable. It increases the value of `$var` by 1 before the statement is executed.

3. **$var += 1**: This is a valid way to increment the variable. It adds 1 to the current value of `$var`.

4. **$var =+ 1**: This is not a valid way to increment the variable. The `=+` operator assigns the value of 1 to `$var`, effectively setting it to 1, rather than incrementing it by 1.

Conclusion

The correct answer is: $var =+ 1 is not a valid way to increment a variable in PHP.