<?php
$strings = [
'av. St Joan 128',
'Av. st joan 122',
'av. St joan 212',
'Av. St.joan 121',
'AV. st joan 232'
];
$results = preg_grep('~^[^A-Z]*[A-Z]?[^A-Z]*$~', $strings);
print_r($results);
Array
(
[1] => Av. st joan 122
[2] => av. St joan 212
)
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
Array
(
[1] => Av. st joan 122
[2] => av. St joan 212
)