How does function strcmp() works in php

Question

For this moment I do not understand in which cases I can use function strcmp() and how it actually works.

Here we have several cases with different ways how this function works.

Case 1:

$a = ‘phh’;
$b = ‘pip’;
echo strcmp($a, $b);

// In this case we will get result -1. As I understand it starts to compare letter by letter and when function found difference it starts to compare two values. In this case first difference found in second letter $a[1] is “h” and $b[1] is “i”. Difference between this number is 1 as letter “i” goes after letter “h”. Minus sign we get because $a < $b. Also this function stop to compare after the first difference is found.

Case 2:

$a = ‘php’;
$b = ‘phpphp’;
echo strcmp($a, $b);

// In this case we will get result -3. As I understand first function strcmp() as in first case starts to compare letter by letter and found that first 3 letters of two strings are similar, but as length of string $b is longer then string $a it start count the difference of symbols? $b > $a for 3 symbol so we get result -3.

Answer 1

There are 3 meaningful results. 0, less than 0, greater than 0.

Those results correspond with
0: a === b
< 0: a < b
> 0: a > b

Try to ignore the -3 vs -1 result for strcmp($a, $b) because those values both mean the same thing. Either way, a < b. Without seeing the implementation it is hard to see why the -1 and -3 are different because all the documentation says is the 3 cases above.

This official documentation has more details on the function:
https://www.php.net/manual/en/function.strcmp.php