Move array item with certain key to the first position in an array, PHP
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What's the most elegant way in PHP to move an array element chosen by key to the first position?
Input:

    $arr[0]=0;
    $arr[1]=1;
    $arr[2]=2;
    ....
    $arr[n]=n;
    $key=10;
Output:

    $arr[0]=10;
    $arr[1]=0;
    $arr[2]=1;
    $arr[3]=2;
    ....
    $arr[n]=n;