PHP Sort an Array of Arrays by Key

array-sorting.php

function array_sort_by_key( $array, $key ) {
    $compare = make_key_cmp( $key );
    usort( $array, $compare );
    return $array;
}

function make_key_cmp( $key ) {
    $code  = "if (\$a['$key'] == \$b['$key']) return 0;";
    $code .= "return (\$a['$key'] < \$b['$key']) ? -1 : 1;";
    return create_function( '$a,$b', $code );
}