Write a PHP function to find unique values from multidimensional arrays and flatten them in 0 depth

<?php
function array_flat($my_array) 
    { 
         $fa = array();
		 $l = 0;
        foreach($my_array as $k => $v ) 
        { 
            if( !is_array( $v ) ) 
            { 
               $fa[ ]= $v; 
                
                continue;           
            } 
             $l++; 
            $fa= array_flat( $v, $fa, $l ); 
            $l--; 
      } 
       
        if( $l == 0 ) $fa = array_values( array_unique( $fa ) );         
        return $fa;       
    } 
$tmp = array( 'a' => array( -1,-2, 0, 2, 3 ), 'b' => array( 'c' => array( -1, 0, 2, 0, 3 ) ) ); 
print_r(array_flat($tmp));
?>