Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

Please read all the docs, not just parts of it.

> If given three arguments, this function returns a copy of str where all
> occurrences of each (single-byte) character in from have been translated to the
> corresponding character in to

> If given two arguments, the second should be an array in the form array('from'
> => 'to', ...). The return value is a string where all the occurrences of the
> array keys have been replaced by the corresponding values.

That is, strtr has two different behaviors: character replacement by passing two strings or string replacement by passing one array.

These are replace pairs, see https://3v4l.org/3rfuV

<?php

$str = 'I loved you';
$from = 'love';
$to = 'lOvE';

var_dump($result1 = strtr($str, $from, $to));
var_dump($result2 = strtr($str, [$from[0] => $to[0], $from[1] => $to[1], $from[2] => $to[2], $from[3] => $to[3]]));
var_dump($result2 = strtr($str, [$from => $to]));
var_dump($result1===$result2);//false

You are misreading the docs. It states:

> If given three arguments, this function returns a copy of str where all occurrences of each (single-byte) character in from have been translated to the corresponding character in to.

It says, "of each character". So all your lowercase "o" and "e" will be uppercased in your example.