Idempotent¶
Idempotent is said of an operation, which yields always the same result after the first call. In other words, repeating the operation does not produce a different result beyond the initial application.
This is the case of strtolower() and strtoupper(): once the string has been made lower case, resp. upper case, calling the same function again on the string will not change the result.
<?php
$string = aBC;
$string1 = strtolower($string); // abc
$string2 = strtolower($string2); // abc
$string3 = strtolower($string3); // abc
$string4 = strtolower($string4); // abc
// ...
?>
See also Idempotence, Designing Idempotent PHP APIs for Distributed Systems and Idempotency: What, Why and How.
Related : strtolower(), Determinism, Useless
