Description:
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Specifying any IP address for bindto in stream_context_set_option() produces an error "(local_addr context option is not a string.)"

Reproduce code:
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$context = stream_context_create ();
stream_context_set_option ($context, 'socket', 'bindto', '127.0.0.1:0');
$contents = file_get_contents ("http://php.net", FALSE, $context);

Expected result:
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Should return the contents of php.net

Actual result:
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Warning: file_get_contents(http://php.net/): failed to open stream: local_addr context option is not a string.