Description:
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This code should delete all non-alphanumeric signs (except spaces).
If you have latin special chars like "?", on the linux machine they are deleted. On a win environment using same php version they are kept as alnum. The deb machine runs with ISO-8859-1 charset.

Reproduce code:
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$somePhrase = 'i don\'t know why, but many people know ?ber';
echo preg_replace('/[^[:alnum:][:space:]]/', '', $somePhrase);

Expected result:
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i dont know why but many people know ?ber

Actual result:
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i dont know why but many people know ber