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<?php $refs = array(); function wrap( $arr){ // Need to clear out the global references array, I chose to do this here global $refs; $refs = array(); test( $arr); } function test( $arr){ global $refs; $refs[] = $arr; foreach( $arr as $v) { if( in_array( $v, $refs)) { print 'ref, '; } else { if( is_array( $v)) { test( $v); } else { print $v . ', '; } } } } echo "Array 1:\n"; $array1 = array(1, 2, 3); $array1[4] = &$array1; wrap( $array1); echo "\nArray 2:\n"; $array2 = array(1, 2, 3, array(1, 2, 3)); $array2[2] = &$array2; wrap( $array2); echo "\nArray 3:\n"; $array3 = array(1, 2, 3, array(1, 2, 3)); $array3[3][1] = &$array3; wrap( $array3);