PHP true/false and 0/1 judgment

Follow the following rules:
a. You cannot use 0/1 instead of true/false. In PHP, this is not equal;
b. Do not use non-zero expressions, variables or methods to directly perform true/false judgments, but must use strict complete true/false judgments;
For example: do not use if ($a) or if (checka()) but use if (FALSE != $a)or if (FALSE != check())