PHP - How can I sort this multi dimensional array by sum value?
<p>How can I sort this array by the sum value of each set in the deepest nested array?</p>

<pre><code>$arr = Array(
    Array(
        'I am the first string.',
        Array(
            Array( 'round', 1, 1 ),
            Array( 'rhythm', 1, 1 )
        )
    ),
    Array(
        'I am the second string',
        Array(
            Array( 'cps', 1, 1 ),
            Array( 'Hz', 1, 3 ),
            Array( 'hertz', 1, 1 )
        )
    ),
    Array(
        'I am the third string.',
        Array(
            Array( 'uucps', 1, 1 ),
            Array( 'uuHz', 1, 2 ),
            Array( 'uuhertz', 1, 1 )
        )
    )

);
</code></pre>

<p>I need to sort the second dimension of arrays by the sum value of third key of the deepest set(third dimension). </p>

<p>So the end result will look like this:</p>

<pre><code>$arr = Array(
    Array(
        'I am the second string',
        Array(
            Array( 'cps', 1, 1 ),
            Array( 'Hz', 1, 3 ),
            Array( 'hertz', 1, 1 )
        )
    ),
    Array(
        'I am the third string.',
        Array(
            Array( 'uucps', 1, 1 ),
            Array( 'uuHz', 1, 2 ),
            Array( 'uuhertz', 1, 1 )
        )
    ),
    Array(
        'I am the first string.',
        Array(
            Array( 'round', 1, 1 ),
            Array( 'rhythm', 1, 1 )
        )
    )

);
</code></pre>

<p>I know that usort might be my best bet but I can't seems to make it work for my use case.</p>