Bool queries can be easily constructed using the client. For example, this query:

curl -XGET 'localhost:9200/my_index/my_type/_search' -d '{
    "query" : {
        "bool" : {
            "must": [
                {
                    "match" : { "testField" : "abc" }
                },
                {
                    "match" : { "testField2" : "xyz" }
                }
            ]
        }
    }
}'

​

Would be structured like this (Note the position of the square brackets):

$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'bool' => [
                'must' => [
                    [ 'match' => [ 'testField' => 'abc' ] ],
                    [ 'match' => [ 'testField2' => 'xyz' ] ],
                ]
            ]
        ]
    ]
];

$results = $client->search($params);

​

Notice that the must clause accepts an array of arrays. This will be serialized into an array of JSON objects internally, so the final resulting output will be identical to the curl example. For more details about arrays vs objects in PHP, see Dealing with JSON Arrays and Objects in PHP.