note 45554 modified in language.references.pass by danbrown

Sometimes we need functions for building or modifying arrays whose elements are to be references to other variables (arrays or objects for instance). In this example, I wrote two functions 'tst' and 'tst1' that perform this task. Note how the functions are written, and how they are used. <?php function tst(&$arr, $r) { // The argument '$arr' is declared to be passed by reference, // but '$r' is not; // however, in the function's body, we use a reference to // the '$r' argument array_push($arr, &$r); // Alternatively, this also could be $arr[] = &$r (in this case) } $arr0 = array(); // an empty array $arr1 = array(1,2,3); // the array to be referenced in $arr0 // Note how we call the function: tst($arr0, &$arr1); // We are passing a reference to '$arr1' in the call ! print_r($arr0); // Contains just the reference to $arr1 array_push($arr0, 5); // we add another element to $arr0 array_push($arr1, 18); // we add another element to $arr1 as well print_r($arr1); print_r($arr0); // Changes in $arr1 are reflected in $arr0 // ----------------------------------------- // A simpler way to do this: function tst1(&$arr, &$r) { // Both arguments '$arr' and '$r" are declared to be passed by // reference, // again, in the function's body, we use a reference to // the '$r' argument array_push($arr, &$r); // Alternatively, this also could be $arr[] = &$r (in this case) } $arr0 = array(); // an empty array $arr1 = array(1,2,3); // the array to be referenced in $arr0 // Note how we call the function: tst1($arr0, $arr1); // 'tst1' understands '$r' is a reference to '$arr1' echo "-------- 2nd. alternative ------------ <br>\n"; print_r($arr0); // Contains just the reference to $arr1 array_push($arr0, 5); // we add another element to $arr0 array_push($arr1, 18); print_r($arr1); print_r($arr0); // Changes in $arr1 are reflected in $arr0 // This outputs: // X-Powered-By: PHP/4.1.2 // Content-type: text/html // // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // ) // // ) // Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // // [1] => 5 // ) // -------- 2nd. alternative ------------ // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // ) // // ) // Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // // [1] => 5 // ) ?> In both cases we get the same result. I hope this is somehow useful Sergio. --was-- Sometimes we need functions for building or modifying arrays whose elements are to be references to other variables (arrays or objects for instance). In this example, I wrote two functions 'tst' and 'tst1' that perform this task. Note how the functions are written, and how they are used. <? function tst(&$arr, $r) { // The argument '$arr' is declared to be passed by reference, // but '$r' is not; // however, in the function's body, we use a reference to // the '$r' argument array_push($arr, &$r); // Alternatively, this also could be $arr[] = &$r (in this case) } $arr0 = array(); // an empty array $arr1 = array(1,2,3); // the array to be referenced in $arr0 // Note how we call the function: tst($arr0, &$arr1); // We are passing a reference to '$arr1' in the call ! print_r($arr0); // Contains just the reference to $arr1 array_push($arr0, 5); // we add another element to $arr0 array_push($arr1, 18); // we add another element to $arr1 as well print_r($arr1); print_r($arr0); // Changes in $arr1 are reflected in $arr0 // ----------------------------------------- // A simpler way to do this: function tst1(&$arr, &$r) { // Both arguments '$arr' and '$r" are declared to be passed by // reference, // again, in the function's body, we use a reference to // the '$r' argument array_push($arr, &$r); // Alternatively, this also could be $arr[] = &$r (in this case) } $arr0 = array(); // an empty array $arr1 = array(1,2,3); // the array to be referenced in $arr0 // Note how we call the function: tst1($arr0, $arr1); // 'tst1' understands '$r' is a reference to '$arr1' echo "-------- 2nd. alternative ------------ <br>\n"; print_r($arr0); // Contains just the reference to $arr1 array_push($arr0, 5); // we add another element to $arr0 array_push($arr1, 18); print_r($arr1); print_r($arr0); // Changes in $arr1 are reflected in $arr0 ?> // This outputs: // X-Powered-By: PHP/4.1.2 // Content-type: text/html // // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // ) // // ) // Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // // [1] => 5 // ) // -------- 2nd. alternative ------------ // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // ) // // ) // Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // Array // ( // [0] => Array // ( // [0] => 1 // [1] => 2 // [2] => 3 // [3] => 18 // ) // // [1] => 5 // ) In both cases we get the same result. I hope this is somehow useful Sergio. http://php.net/manual/en/language.references.pass.php