By default, PHP Autocomplete allows selection of a single value. To select multiple values, call enable_multiple() method and pass true.
$data =
array(
array('id'=>1, 'text'=>'Japan'),
array('id'=>2, 'text'=>'USA'),
array('id'=>3, 'text'=>'Hong Kong'),
array('id'=>4, 'text'=>'Canada'),
array('id'=>5, 'text'=>'Brazil')
);
$pac = new C_PhpAutocomplete('country', $data);
$pac -> enable_multiple(true);
$pac -> display();
?>
<input type="hidden" id="country">
Note that When attached to a <select> element this value will be ignored and <select> multiple attribute will be used instead.
$pac = new C_PhpAutocomplete('country');
$pac -> enable_multiple(true); // will be ignored
$pac -> display('SELECT');
?>
<select id="country" multiple>
<option id="1">Japan</option>
<option id="2">USA</option>
<option id="3">Hong Kong</option>
<option id="4">Canada</option>
<option id="5">Brazil</option>
</select>