You may try with the following simple code. Note, that if you want to include a literal character in the format, you need to escape it with a backslash (\). The result from date_create_from_format() / DateTime::createFromFormat() call is a DateTime object representing the date and time specified by the time string, so you need to format it appropriately.
Procedural:
<?php
$datetime = date_create_from_format('Y-m-d\TH:i:sP', '2020-05-26T11:03:00+03:00');
echo date_format($datetime, 'g:iA');
?>
Object-oriented:
<?php
$datetime = DateTime::createFromFormat('Y-m-d\TH:i:sP', '2020-05-26T11:03:00+03:00');
echo $datetime->format('g:iA');
?>
Output:
11:03AM
strtotime()