php - USort Multi Index Array - Doesn't Return Correctly -

i'm having trouble phps usort() function. have multi-indexed array looks this:

array (     [0] => array         (             [0] => array                 (                     [title] => c                     [more_fields] => '...'                 )              [1] => array                 (                     [title] =>                     [more_fields] => '...'                 )              [2] => array                 (                     [title] => b                     [more_fields] => '...'                 )              [3] => array                 (                     [title] => xz                     [more_fields] => '...'                 )          ) ) 

i'm trying loop through array , sort each index title index. here's code without of test inputs:

foreach( $my_arr $arr ) {     if( count( $arr ) > 1 ) {         usort( $arr, function( $a, $b ) {             return strcasecmp( $a['title'], $b['title'] );         } );     } } 

now expect work, , know i'm hitting right indexes, if echo out $a['title'] , $b['title'] before return data looks like:

a _ c | xz _ | b _ | c _ | b _ c | xz _ b | c _ b | xz _ c 

that's fine , dandy, once foreach finished, array unchanged. looks like, looking @ php docs usort() passing array reference , returning booleans on completion. missing in usort() keeps leaving array unchanged?

foreach works on copy of array. modify actual array need reference value (notice &):

foreach( $my_arr &$arr ) { 

or should able use key , actual array $my_arr[$key]:

foreach( $my_arr $key => $arr ) {     if( count( $arr ) > 1 ) {         usort( $my_arr[$key], function( $a, $b ) {             return strcasecmp( $a['title'], $b['title'] );         } );     } }