The use of operators pairs ( =+, =- or =! ) where the reversed, single operator was meant (+=, -= or !=) will compile and run, but not produce the expected results.

This rule raises an issue when =+, =-, or =! is used without any spacing between the two operators and when there is at least one whitespace character after.

Noncompliant Code Example

$target = -5;
$num = 3;

$target =- $num;  // Noncompliant; target = -3. Is that really what's meant?
$target =+ $num; // Noncompliant; target = 3

Compliant Solution

$target = -5;
$num = 3;

$target = -$num;  // Compliant; intent to assign inverse value of num is clear
$target += $num;