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Going on with general cleanups. Removing the whole outdated

Browse source 
and long ago commented single/multidimensional array parts.
Adding more examples, adding some points that were in TODO.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@102563 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Gabor Hojtsy 2002-11-04 17:34:52 +00:00
parent 69e4f3f0be
commit 7caa8cc18e
1 changed files with 241 additions and 366 deletions
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607
language/types.xml
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@ -1,5 +1,5 @@
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.94 $ -->
<!-- $Revision: 1.95 $ -->
<chapter id="language.types">
<title>Types</title>
@ -907,7 +907,7 @@ $great = 'fantastic';
echo "This is { $great}"; // won't work, outputs: This is { fantastic}
echo "This is {$great}"; // works, outputs: This is fantastic
echo "This square is {$square->width}00 centimeters broad.";
echo "This works: {$arr[4][3]}";
echo "This works: {$arr[4][3]}";
// This is wrong for the same reason
// as $foo[bar] is wrong outside a string.
@ -946,35 +946,15 @@ echo "I'd like to have another {${ strrev('reeb') }}, hips";
<example>
<title>Some string examples</title>
<programlisting role="php">
<!-- TODO: either move these examples to a example section,
as with arrays, or distribute them under the applicable
sections. -->
<![CDATA[
<?php
/* Assigning a string. */
$str = "This is a string";
/* Appending to it. */
$str = $str . " with some more text";
/* Another way to append, includes an escaped newline. */
$str .= " and a newline at the end.\n";
/* This string will end up being '<p>Number: 9</p>' */
$num = 9;
$str = "<p>Number: $num</p>";
/* This one will be '<p>Number: $num</p>' */
$num = 9;
$str = '<p>Number: $num</p>';
/* Get the first character of a string */
// Get the first character of a string
$str = 'This is a test.';
$first = $str{0};
/* Get the last character of a string. */
// Get the last character of a string.
$str = 'This is still a test.';
$last = $str{strlen($str)-1};
$last = $str{strlen($str)-1};
?>
]]>
</programlisting>
@ -985,7 +965,7 @@ $last = $str{strlen($str)-1};
</sect2><!-- end syntax -->
<sect2 id="language.types.string.useful-funcs">
<title>Useful functions</title><!-- and operators -->
<title>Useful functions and operators</title>
<para>
Strings may be concatenated using the '.' (dot) operator. Note
that the '+' (addition) operator will not work for this. Please
@ -1013,6 +993,7 @@ $last = $str{strlen($str)-1};
see also the <link linkend="ref.ctype">character type functions</link>.
</simpara>
</sect2>
<sect2 id="language.types.string.casting">
<title>Converting to string</title>
@ -1145,8 +1126,7 @@ echo "\$foo==$foo; type is " . gettype ($foo) . "<br />\n";
This type is optimized in several ways,
so you can use it as a real array, or a list (vector),
hashtable (which is an implementation of a map),
dictionary, <!-- is a map -->
collection,
dictionary, collection,
stack, queue and probably more. Because you can have another
PHP-array as a value, you can also quite easily simulate
trees.
@ -1154,10 +1134,8 @@ echo "\$foo==$foo; type is " . gettype ($foo) . "<br />\n";
<para>
Explanation of those structures is beyond the scope of this manual,
but you'll find at least one example for each of those structures.
For more information about those structures, we refer you to
external literature about this broad topic.
<!-- like goodrich&tamassia: datastructures and algorithmes.
Only, the subtitle is: in Java, and it's quite academic too -->
For more information we refer you to external literature about
this broad topic.
</para>
<sect2 id="language.types.array.syntax">
@ -1170,43 +1148,8 @@ echo "\$foo==$foo; type is " . gettype ($foo) . "<br />\n";
language-construct. It takes a certain number of comma-separated
<literal><replaceable>key</replaceable> =&gt; <replaceable
>value</replaceable></literal>
pairs.
pairs.
</para>
<para>
A <varname>key</varname> is either an <type>integer</type>
or a <type>string</type>.
If a key is the standard representation of an
<type>integer</type>, it will
be interpreted as such (i.e. <literal>"8"</literal> will be interpreted
as <literal>8</literal>, while
<literal>"08"</literal> will be interpreted as <literal>"08"</literal>).
</para>
<para>
A value can be anything.
</para>
<para>
If you omit a key, the maximum of the integer-indices is taken, and
the new key will be that maximum + 1. As integers can be negative,
this is also true for negative indices. Having e.g. the highest index
being <literal>-6</literal> will result in being <literal>-5</literal>
the new key. If no integer-indices exist
yet, the key will be <literal>0</literal> (zero). If you specify a key
that already has a value assigned to it, that value will be overwritten.
</para>
<para>
Using <literal>true</literal> as a key will evalute to
<type>integer</type> <literal>1</literal> as key. Using
<literal>false</literal> as a key will evalute to <type>integer</type>
<literal>0</literal> as key. Using <literal>NULL</literal> as a key
will evaluate to an empty string. Using an emptry string as key will
create (or overwrite) a key with an empty string and its value, it is
not the same as using empty brackets.
</para>
<para>
You cannot use arrays or objects as keys. Doing so will result in a
warning: <literal>Illegal offset type</literal>.
</para>
<para>
<synopsis>
array( <optional> <replaceable>key</replaceable> =&gt; </optional> <replaceable
@ -1218,19 +1161,79 @@ array( <optional> <replaceable>key</replaceable> =&gt; </optional> <replaceable
// <replaceable>value</replaceable> can be anything
</synopsis>
</para>
<para>
<informalexample>
<programlisting role="php">
<![CDATA[
array("foo" => "bar", 12 => true);
]]>
</programlisting>
</informalexample>
</para>
<para>
A <varname>key</varname> is either an <type>integer</type>
or a <type>string</type>. If a key is the standard representation
of an <type>integer</type>, it will be interpreted as such (i.e.
<literal>"8"</literal> will be interpreted as <literal>8</literal>,
while <literal>"08"</literal> will be interpreted as
<literal>"08"</literal>). There are no different indexed and
associative array types in PHP, there is only one array type,
which can both contain integer and string indices.
</para>
<para>
A value can be of any PHP type.
<informalexample>
<programlisting role="php">
<![CDATA[
array("somearray" => array(6 => 5, 13 => 9, "a" => 43));
]]>
</programlisting>
</informalexample>
</para>
<para>
If you omit a key, the maximum of the integer-indices is taken, and
the new key will be that maximum + 1. As integers can be negative,
this is also true for negative indices. Having e.g. the highest index
being <literal>-6</literal> will result in being <literal>-5</literal>
the new key. If no integer-indices exist
yet, the key will be <literal>0</literal> (zero). If you specify a key
that already has a value assigned to it, that value will be overwritten.
<informalexample>
<programlisting role="php">
<![CDATA[
// This array is the same as ...
array(5 => 43, 32, 56, "b" => 12);
// ...this array
array(5 => 43, 6 => 32, 7 => 56, "b" => 12);
]]>
</programlisting>
</informalexample>
</para>
<para>
Using &true; as a key will evalute to
<type>integer</type> <literal>1</literal> as key. Using
&false; as a key will evalute to <type>integer</type>
<literal>0</literal> as key. Using <literal>NULL</literal> as a key
will evaluate to an empty string. Using an emptry string as key will
create (or overwrite) a key with an empty string and its value, it is
not the same as using empty brackets.
</para>
<para>
You cannot use arrays or objects as keys. Doing so will result in a
warning: <literal>Illegal offset type</literal>.
</para>
</sect3>
<sect3 id="language.types.array.syntax.modifying">
<title>Creating/modifying with square-bracket syntax</title>
<para>
You can also modify an existing array, by explicitly setting
values.
values in it.
</para>
<para>
This is done by assigning values to the array while specifying the
key in brackets. You can also
omit the key,
add an empty pair
key in brackets. You can also omit the key, add an empty pair
of brackets ("<literal>[]</literal>") to the variable-name in that case.
<synopsis>
$arr[<replaceable>key</replaceable>] = <replaceable>value</replaceable>;
@ -1240,41 +1243,57 @@ $arr[] = <replaceable>value</replaceable>;
// <replaceable>value</replaceable> can be anything
</synopsis>
If <varname>$arr</varname> doesn't exist yet, it will be created.
So this is also
an alternative way to specify an array.
So this is also an alternative way to specify an array.
To change a certain value, just assign a new value
to it.
If you want to remove a key/value pair, you need to
<function>unset</function> it.
to an element specified with its key. If you want to
remove a key/value pair, you need to <function>unset</function> it.
<informalexample>
<programlisting role="php">
<![CDATA[
$arr = array(5 => 1, 12 => 2);
$arr[] = 56; // This is the same as $arr[13] = 56;
// at this point of the script
$arr["x"] = 42; // This adds a new element to
// the array with key "x"
unset($arr[5]); // This removes the element from the array
unset($arr); // This deletes the whole array
]]>
</programlisting>
</informalexample>
</para>
</sect3>
</sect2><!-- end syntax -->
<sect2 id="language.types.array.useful-funcs">
<title>Useful functions</title>
<para>
There are quite some useful function for working
with arrays, see the <link linkend="ref.array">array-functions</link>
section.
with arrays, see the <link linkend="ref.array">array
functions</link> section.
</para>
<note>
<para>
The <function>unset</function> function allows unsetting keys of an
array. Be aware that the array will NOT be reindexed.
array. Be aware that the array will NOT be reindexed. If you only
use "usual integer indices" (starting from zero, increasing by one),
you can achive the reindex effect by using <function>array_values</function>.
<informalexample>
<programlisting role="php">
<![CDATA[
$a = array( 1 => 'one', 2 => 'two', 3 => 'three' );
unset( $a[2] );
$a = array(1 => 'one', 2 => 'two', 3 => 'three');
unset($a[2]);
/* will produce an array that would have been defined as
$a = array( 1=>'one', 3=>'three');
$a = array(1 => 'one', 3 => 'three');
and NOT
$a = array( 1 => 'one', 2 => 'three');
*/
$a = array(1 => 'one', 2 =>'three');
*/
$b = array_values($a);
// Now b is array(1 => 'one', 2 =>'three')
]]>
</programlisting>
</informalexample>
@ -1286,8 +1305,6 @@ unset( $a[2] );
control structure exists specifically for arrays. It
provides an easy way to traverse an array.
</para>
</sect2>
<sect2 id="language.types.array.donts">
@ -1312,7 +1329,8 @@ echo $foo[bar];
this code has an undefined constant (bar) rather than a string ('bar' -
notice the quotes), and PHP may in future define constants which,
unfortunately for your code, have the same name. It works, because the
undefined constant gets converted to a string of the same name.
undefined constant gets converted to a string of the same name
automatically for backward compatibility reasons.
</para>
<para>
As stated in the <link linkend="language.types.array.syntax"
@ -1322,21 +1340,21 @@ echo $foo[bar];
<informalexample>
<programlisting role="php">
<![CDATA[
echo $arr[ foo(true) ];
echo $arr[foo(true)];
]]>
</programlisting>
</informalexample>
This is an example of using a function return value
as the array index. PHP knows also about constants,
and you may have seen the
<literal>E_*</literal> before.
as the array index. PHP also knows about constants,
as you may have seen the <literal>E_*</literal> ones
before.
<informalexample>
<programlisting role="php">
<![CDATA[
$error_descriptions[E_ERROR] = "A fatal error has occured";
$error_descriptions[E_ERROR] = "A fatal error has occured";
$error_descriptions[E_WARNING] = "PHP issued a warning";
$error_descriptions[E_NOTICE] = "This is just an informal notice";
$error_descriptions[E_NOTICE] = "This is just an informal notice";
]]>
</programlisting>
</informalexample>
@ -1367,7 +1385,8 @@ $error_descriptions[8] = "This is just an informal notice";
<title>So why is it bad then?</title>
<para>
At some point in the future, the PHP team might want to add another
constant or keyword, and then you get in trouble. For example,
constant or keyword, or you may introduce another constant into your
application, and then you get in trouble. For example,
you already cannot use the words <literal>empty</literal> and
<literal>default</literal> this way, since they are special
<link linkend="reserved">reserved keywords</link>.
@ -1377,14 +1396,41 @@ $error_descriptions[8] = "This is just an informal notice";
When you turn <link linkend="function.error-reporting"
>error_reporting</link> to <literal>E_ALL</literal>,
you will see that PHP generates notices whenever an
<literal>index</literal> is used which is not defined
(put the line <literal>error_reporting(E_ALL);</literal>
in your script).
<literal>index</literal> is used which is not defined.
Consider this script:
<informalexample>
<programlisting role="php">
<![CDATA[
<?php
// Turn on the display of all errors
error_reporting(E_ALL);
// Define the test array
$abc = array("x" => "y");
// Access element with the *bad* method
echo $abc[x];
?>
]]>
</programlisting>
</informalexample>
The output is:
<informalexample>
<programlisting>
<![CDATA[
<br />
<b>Notice</b>: Use of undefined constant x - assumed 'x' in <b>/path/to/script.php</b> on
line <b>10</b><br />
]]>
</programlisting>
</informalexample>
</simpara>
</note>
<note>
<simpara>
Inside a double-quoted <type>string</type>, an other syntax
Inside a double-quoted <type>string</type>, another syntax
is valid. See <link linkend="language.types.string.parsing"
>variable parsing in strings</link> for more details.
</simpara>
@ -1393,6 +1439,26 @@ $error_descriptions[8] = "This is just an informal notice";
</sect3>
</sect2>
<sect2 id="language.types.array.casting">
<title>Converting to array</title>
<para>
For any of the types: integer, float, string, boolean and resource,
if you convert a value to an array, you get an array with one element
(with index 0), which is the scalar value you started with.
</para>
<para>
If you convert an object to an array, you get the properties (member
variables) of that object as the array's elements. The keys are the
member variable names.
</para>
<para>
If you convert a &null; value to an array, you get an empty array.
</para>
</sect2>
<sect2 id="language.types.array.examples">
<title>Examples</title>
<para>
@ -1404,24 +1470,24 @@ $error_descriptions[8] = "This is just an informal notice";
<programlisting role="php">
<![CDATA[
// this
$a = array( 'color' => 'red'
, 'taste' => 'sweet'
, 'shape' => 'round'
, 'name' => 'apple'
, 4 // key will be 0
$a = array( 'color' => 'red',
'taste' => 'sweet',
'shape' => 'round',
'name' => 'apple',
4 // key will be 0
);
// is completely equivalent with
$a['color'] = 'red';
$a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name'] = 'apple';
$a['name'] = 'apple';
$a[] = 4; // key will be 0
$b[] = 'a';
$b[] = 'b';
$b[] = 'c';
// will result in the array array( 0 => 'a' , 1 => 'b' , 2 => 'c' ),
// will result in the array array(0 => 'a' , 1 => 'b' , 2 => 'c'),
// or simply array('a', 'b', 'c')
]]>
</programlisting>
@ -1433,40 +1499,38 @@ $b[] = 'c';
<programlisting role="php">
<![CDATA[
// Array as (property-)map
$map = array( 'version' => 4
, 'OS' => 'Linux'
, 'lang' => 'english'
, 'short_tags' => true
$map = array( 'version' => 4,
'OS' => 'Linux',
'lang' => 'english',
'short_tags' => true
);
// strictly numerical keys
$array = array( 7
, 8
, 0
, 156
, -10
$array = array( 7,
8,
0,
156,
-10
);
// this is the same as array( 0 => 7, 1 => 8, ...)
// this is the same as array(0 => 7, 1 => 8, ...)
$switching = array( 10 // key = 0
, 5 => 6
, 3 => 7
, 'a' => 4
, 11 // key = 6 (maximum of integer-indices was 5)
, '8' => 2 // key = 8 (integer!)
, '02' => 77 // key = '02'
, 0 => 12 // the value 10 will be overwritten by 12
$switching = array( 10, // key = 0
5 => 6,
3 => 7,
'a' => 4,
11, // key = 6 (maximum of integer-indices was 5)
'8' => 2, // key = 8 (integer!)
'02' => 77, // key = '02'
0 => 12 // the value 10 will be overwritten by 12
);
// empty array
$empty = array();
]]>
<!-- TODO example of
- mixed keys
- overwriting keys
- integer keys as string
- using vars/functions as key/values
- mixed skipping
- warning about references
-->
</programlisting>
</example>
@ -1475,9 +1539,9 @@ $empty = array();
<title>Collection</title>
<programlisting role="php">
<![CDATA[
$colors = array('red','blue','green','yellow');
$colors = array('red', 'blue', 'green', 'yellow');
foreach ( $colors as $color ) {
foreach ($colors as $color) {
echo "Do you like $color?\n";
}
@ -1509,7 +1573,7 @@ foreach ($colors as $key => $color) {
// won't work:
//$color = strtoupper($color);
//works:
// works:
$colors[$key] = strtoupper($color);
}
print_r($colors);
@ -1549,13 +1613,12 @@ Array
</example>
</para>
<example>
<title>Filling real array</title>
<title>Filling an array</title>
<programlisting role="php">
<![CDATA[
// fill an array with all items from a directory
$handle = opendir('.');
while ($file = readdir($handle))
{
while ($file = readdir($handle)) {
$files[] = $file;
}
closedir($handle);
@ -1564,8 +1627,10 @@ closedir($handle);
</example>
<para>
Arrays are ordered. You can also change the order using various
sorting-functions. See <link linkend="ref.array">array-functions</link>
for more information.
sorting-functions. See the <link linkend="ref.array">array
functions</link> section for more information. You can count
the number of items in an array using the
<function>count</function> function.
</para>
<example>
<title>Sorting array</title>
@ -1585,228 +1650,50 @@ print_r($files);
<title>Recursive and multi-dimensional arrays</title>
<programlisting role="php">
<![CDATA[
$fruits = array ( "fruits" => array ( "a" => "orange"
, "b" => "banana"
, "c" => "apple"
)
, "numbers" => array ( 1
, 2
, 3
, 4
, 5
, 6
)
, "holes" => array ( "first"
, 5 => "second"
, "third"
$fruits = array ( "fruits" => array ( "a" => "orange",
"b" => "banana",
"c" => "apple"
),
"numbers" => array ( 1,
2,
3,
4,
5,
6,
),
"holes" => array ( "first",
5 => "second",
"third"
)
);
// Some examples to address values in the array above
echo $fruits["holes"][5]; // prints "second"
echo $fruits["fruits"]["a"]; // prints "orange"
unset($fruits["holes"][0]); // remove "first"
// Create a new multi-dimensional array
$juices["apple"]["green"] = "good";
]]>
<!-- quite duplicate...
$a = array(
"apple" => array(
"color" => "red",
"taste" => "sweet",
"shape" => "round"
),
"orange" => array(
"color" => "orange",
"taste" => "tart",
"shape" => "round"
),
"banana" => array(
"color" => "yellow",
"taste" => "paste-y",
"shape" => "banana-shaped"
)
);
-->
</programlisting>
</example>
</sect2>
<!-- TODO
<sect2>
<title>Misc</title>
</sect2>
- example multi-dim with $arr[bla][bla] syntax
- converting to array
- warning about references
- note that assigning is copy (usually...)
-->
<!-- there is no such thing as multi/singel dim arrays (at least in PHP4)
<sect2 id="language.types.array.single-dim">
<title>Single Dimension Arrays</title>
<para>
PHP supports both scalar and associative arrays. In fact, there
is no difference between the two. You can create an array using
the
<function>list</function>
Nope
or <function>array</function>
functions, or you can explicitly set each array element value.
<informalexample>
<programlisting role="php">
$a[0] = "abc";
$a[1] = "def";
$b["foo"] = 13;
</programlisting>
</informalexample>
</para>
<para>
You can also create an array by simply adding values to the
array. When you assign a value to an array variable using empty
brackets, the value will be added onto the end of the array.
<informalexample>
<programlisting role="php">
$a[] = "hello"; // $a[2] == "hello"
$a[] = "world"; // $a[3] == "world"
</programlisting>
</informalexample>
</para>
<para>
Arrays may be sorted using the <function>asort</function>,
<function>arsort</function>, <function>ksort</function>,
<function>rsort</function>, <function>sort</function>,
<function>uasort</function>, <function>usort</function>, and
<function>uksort</function> functions depending on the type of
sort you want.
</para>
<para>
You can count the number of items in an array using the
<function>count</function> function.
</para>
<para>
You can traverse an array using <function>next</function> and
<function>prev</function> functions. Another common way to
traverse an array is to use the <function>each</function>
function.
</para>
</sect2>
<sect2 id="language.types.array.multi-dim">
<title>Multi-Dimensional Arrays</title>
<para>
Multi-dimensional arrays are actually pretty simple. For each
dimension of the array, you add another [key] value to the end:
<informalexample>
<programlisting role="php">
$a[1] = $f; # one dimensional examples
$a["foo"] = $f;
$a[1][0] = $f; # two dimensional
$a["foo"][2] = $f; # (you can mix numeric and associative indices)
$a[3]["bar"] = $f; # (you can mix numeric and associative indices)
$a["foo"][4]["bar"][0] = $f; # four dimensional!
</programlisting>
</informalexample>
</para>
<para>
In PHP 3 it is not possible to reference multidimensional arrays
directly within strings. For instance, the following will not
have the desired result:
<informalexample>
<programlisting role="php">
$a[3]['bar'] = 'Bob';
echo "This won't work: $a[3][bar]";
</programlisting>
</informalexample>
In PHP 3, the above will output <computeroutput>This won't work:
Array[bar]</computeroutput>. The string concatenation operator,
however, can be used to overcome this:
You should be aware, that array assignment always involves
value copying. You need to use the reference operator to copy
an array by reference.
<informalexample>
<programlisting role="php">
$a[3]['bar'] = 'Bob';
echo "This will work: " . $a[3]['bar'];
$arr1 = array(2, 3);
$arr2 = $arr1;
$arr2[] = 4; // $arr2 is changed,
// $arr1 is still array(2,3)
$arr3 = &$arr1;
$arr3[] = 4; // now $arr1 and $arr3 are the same
</programlisting>
</informalexample>
</para>
<para>
In PHP 4, however, the whole problem may be circumvented by
enclosing the array reference (inside the string) in curly
braces:
<informalexample>
<programlisting role="php">
$a[3]['bar'] = 'Bob';
echo "This will work: {$a[3][bar]}";
</programlisting>
</informalexample>
</para>
<para>
You can "fill up" multi-dimensional arrays in many ways, but the
trickiest one to understand is how to use the
<function>array</function> command for associative arrays. These
two snippets of code fill up the one-dimensional array in the
same way:
<informalexample>
<programlisting role="php">
# Example 1:
$a["color"] = "red";
$a["taste"] = "sweet";
$a["shape"] = "round";
$a["name"] = "apple";
$a[3] = 4;
# Example 2:
$a = array(
"color" => "red",
"taste" => "sweet",
"shape" => "round",
"name" => "apple",
3 => 4
);
</programlisting>
</informalexample>
</para>
<para>
The <function>array</function> function can be nested for
multi-dimensional arrays:
<informalexample>
<programlisting role="php">
&lt;?php
$a = array(
"apple" => array(
"color" => "red",
"taste" => "sweet",
"shape" => "round"
),
"orange" => array(
"color" => "orange",
"taste" => "tart",
"shape" => "round"
),
"banana" => array(
"color" => "yellow",
"taste" => "paste-y",
"shape" => "banana-shaped"
)
);
echo $a["apple"]["taste"]; # will output "sweet"
?>
</programlisting>
</informalexample>
</para>
</sect2>
-->
</sect1>
<sect1 id="language.types.object">
@ -2220,19 +2107,19 @@ if ($fst === $str) {
<simpara><link linkend="language.types.integer.casting">Converting to
integer</link></simpara>
</listitem>
<listitem>
<simpara><link linkend="language.types.string.casting">Converting to
string</link></simpara>
</listitem>
<!-- don't exist yet
<listitem>
<simpara><link linkend="language.types.float.casting">Converting to
float</link></simpara>
</listitem>
<listitem>
<simpara><link linkend="language.types.string.casting">Converting to
string</link></simpara>
</listitem>
<listitem>
<simpara><link linkend="language.types.array.casting">Converting to
array</link></simpara>
</listitem>
<!-- don't exist yet
<listitem>
<simpara><link linkend="language.types.object.casting">Converting to
object</link></simpara>
@ -2249,18 +2136,6 @@ if ($fst === $str) {
</itemizedlist>
</para>
<para>
<!-- TODO: move to 'converting to array' -->
When casting from a scalar or a string variable to an array, the
variable will become the first element of the array:
<informalexample>
<programlisting role="php">
$var = 'ciao';
$arr = (array) $var;
echo $arr[0]; // outputs 'ciao'
</programlisting>
</informalexample>
</para>
<para>
<!-- TODO: move to 'converting to object' -->
When casting from a scalar or a string variable to an object, the