Description:
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PHP 5.1 don't know some timezones that was avaible in PHP 5.0. At first, the setted TZ come from a SPL function ( date() ) and afterwards saying it doesn't know it.

Ans why will this code bellow set 'UTC' in the ENV var instead of the before setted CEST?

Reproduce code:
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<?php
error_reporting(E_ALL);

echo getenv('TZ') . "\n";
echo date('T') . "\n";
putenv('TZ=' . date('T'));
echo getenv('TZ') . "\n";
echo date('T') . "\n";

Expected result:
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CEST
CEST
UTC

Actual result:
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CEST
CEST

Notice: date(): Timezone setting (date.timezone) or TZ environment variable contains an unknown timezone. in /home/Thomas/test.php on line 9
UTC