I have this array in PHP:

array(
    [0] => array( 'username' => 'user1' )
    [1] => array( 'username' => 'user2' )
)

If I have the 'username' string how can I get the index value as a number?

Example, if I have 'user1' how can I get 0?

php arrays multidimensional-array key
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