What are the potential reasons why 2 out of 4 identical variables are not functioning properly in a PHP code?

The potential reasons why 2 out of 4 identical variables are not functioning properly in a PHP code could be due to syntax errors, variable scope issues, or incorrect variable assignments. To solve this issue, check for any typos or syntax errors in the variable names, ensure that the variables are properly declared and initialized within the correct scope, and verify that the correct values are being assigned to each variable.

// Incorrect variable assignments
$variable1 = "value1";
$variable2 = "value2";
$variable3 = "value3";
$variable4 = "value4";

// Correct variable assignments
$variable1 = "value1";
$variable2 = "value2";
$variable3 = "value3";
$variable4 = "value4";