返回值

值通过使用可选的返回语句返回。任何类型都可以返回，其中包括列表和对象。这导致函数立即结束它的运行，并且将控制权传递回它被调用的行。更多信息见 return()。

例子 17-11. return() 的用法
<?php function square($num) { return $num * $num; } echo square(4); // outputs '16'. ?>

函数不能返回多个值，但为了获得简单的结果，可以返回一个列表。

例子 17-12. 返回一个数组以得到多个返回值
<?php function small_numbers() { return array (0, 1, 2); } list ($zero, $one, $two) = small_numbers(); ?>

从函数返回一个引用，必须在函数声明和指派返回值给一个变量时都使用引用操作符 & ：

例子 17-13. 由函数返回一个引用
<?php function &returns_reference() { return $someref; } $newref =& returns_reference(); ?>

有关引用的更多信息, 请查看引用的解释。

add a note User Contributed Notes

Trevor Blackbird > yurab.com
19-Apr-2006 07:36


You can also use the compact-extract pair to return multiple values:



<?php



function Composite($x, $y) {

    $sum = $x + $y;

    $dif = $x - $y;

    return compact('sum', 'dif');

}



extract(Composite(3, 4));

echo $sum;

echo $dif;



?>

nick at itomic.com
04-Aug-2003 03:56


Functions which return references, may return a NULL value. This is inconsistent with the fact that function parameters passed by reference can't be passed as NULL (or in fact anything which isnt a variable).



i.e.



<?php



function &testRet()

{

    return NULL;

}



if (testRet() === NULL)

{

    echo "NULL";

}

?>



parses fine and echoes NULL

rusty at socrates dot berkeley dot edu
18-Jul-2003 05:48


Here's a sick idea.  When a function returns no value, if you assign its return value to a variable that variable will be unset.  So instead of returning -1 on error just return with no value.



For example,



function myfunc($myvar) {

  if ($myvar == "abc")

    return(1);



  if ($myvar == "xyz")

    return(2);



  return;

}



$abc = myfunc("def");



if (isset($abc))

   echo("a-ok");

else

  echo("oops");

LouisGreen at pljg dot freeserve dot co dot uk
26-Mar-2003 02:13


It seems that when you wish to export a varible, you can do it as return $varible, return an array(), or globalise it. If you return something, information for that varible can only travel one way when the script is running, and that is out of the function. 





function fn() {


   $varible = "something";





  return $varible;


}





echo fn();


OR


$newvarible = fn();





Although if global was used, it creates a pointer to a varible, whether it existed or not, and makes whatever is created in the function linked to that global pointer. So if the pointer was global $varible, and then you set a value to $varible, it would then be accessible in the global scope. But then what if you later on in the script redefine that global to equal something else. This means that whatever is put into the global array, the information that is set in the pointer, can be set at any point (overiden). Here is an example that might make this a little clearer:





function fn1() {





   global $varible; // Pointer to the global array


   $varible = "something";


}





fn1();


echo $varible; // Prints something


$varible = "12345";


echo $varible; // Prints 12345





function fn2() {





   global $varible; // Pointer to the global array


   echo $varible;


}





fn2(); // echos $varible which contains "12345"





Basically with the global array, you can set it refer to something already defined or set it to something, (a pointer) such as varible you plan to create in the function, and later possibly over ride the pointer with something else.

ian at NO_SPAM dot verteron dot net
15-Jan-2003 08:28


In reference to the poster above, an additional (better?) way to return multiple values from a function is to use list(). For example:



function fn($a, $b)

{

   # complex stuff



   return array(

      $a * $b,

      $a + $b,

   );

}



list($product, $sum) = fn(3, 4);



echo $product; # prints 12

echo $sum; # prints 7

devinemke at yahoo dot com
27-Jun-2002 02:45


A function can only return one value, but that value can be an array or other compound value.  If you want to just define several variables into the global scope within your function you can do two things:



1. return an array from your function and then run the extract() function



$result_array = test ();

extract ($result_array);



2. Or you can just append the variables to the $GLOBALS array:



$array = array ('first' => 'john', 'middle' => 'q', 'last' => 'public');

function upper_case () {

global $array;

foreach ($array as $key => $value)

{

$GLOBALS[$key] = strtoupper ($value);

}

}



upper_case ();

echo "$first $middle $last";

// returns JOHN Q PUBLIC



In this second example you can create multiple values without necessarily returning anything from the function.  This may be handy for applying several functions (stripslashes, trim, etc..) accross all elements of $_POST or $_GET and then having all of the newly cleaned up variables extracted out for you.

destes at ix dot netcom dot com dot nospam
04-Mar-2002 04:35


One thing to note about returning arrays- the usual "complex variable" syntax will give you a parse error.  For instance, if you have:



function adminstuff() {

    mysql_connect('localhost', 'user', 'pass');

    mysql_select_db('mydb');

    $result = mysql_query('SELECT login, pass FROM users);

    $resultrow = mysql_fetch_array( $result );



    # this next line is key:

    return array ({$resultrow['login']}, {$resultrow['pass']});

}



That won't work.  You *can* reference array elements without the curly-braces syntax, i.e.:



return array ($resultrow['login'], $resultrow['pass']);



But you'll get a parse error if you try to use curly braces.  Thanks,



Steve

php at control-escape dot com
26-Apr-2001 03:26


PHP functions that do not explicitly return a value will be 'void', that is, they return 'null'. C programmers will be accustomed to this already, but folks coming from Perl may expect the return value of a function to be the return value of the last expression evaluated inside the function, as is the case with Perl. Not so.

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