javascript - JQuery UI Autocomplete with PHP file source

I am trying to use JQueryUI autocomplete, with data coming from a remote source (another php script). Below is the example given in the demos on the JQueryUI website:

<style>
.ui-autocomplete-loading { background: white url('images/ui-anim_basic_16x16.gif') right center no-repeat; }
</style>
<script>
$(function() {
    function log( message ) {
        $( "<div/>" ).text( message ).prependTo( "#log" );
        $( "#log" ).scrollTop( 0 );
    }

    $( "#birds" ).autocomplete({
        source: "search.php",
        minLength: 2,
        select: function( event, ui ) {
            log( ui.item ?
                "Selected: " + ui.item.value + " aka " + ui.item.id :
                "Nothing selected, input was " + this.value );
        }
    });
});
</script>
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My question is about the PHP script "search.php". Should this script simply return an array?