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Put foreach() into its own section and clarified some stuff.

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Also copied it into the German tree.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@17020 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Torben Wilson 1999-12-11 00:43:25 +00:00
parent 195e0588f7
commit bbc162f979
1 changed files with 105 additions and 46 deletions
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151
language/control-structures.xml
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@ -333,7 +333,8 @@
<programlisting>
for (expr1; expr2; expr3) statement
</programlisting>
</informalexample></para>
</informalexample>
</para>
<simpara>
The first expression (<replaceable>expr1</replaceable>) is evaluated
@ -412,36 +413,96 @@ for (expr1; expr2; expr3) statement
</programlisting>
</informalexample></para>
<para>
Other languages have a foreach statement to traverse an array or
hash. PHP uses the while statement and the <function>list</function>
and <function>each</function> functions for this. See the
documentation for these functions for an example.</para>
<para>
Other languages have a <literal>foreach</literal> statement to
traverse an array or hash. PHP3 has no such construct; PHP4 does
(see <link
linkend="control-structures.foreach">foreach</link>). In PHP3, you
can combine <link linkend="control-structures.while">while</link>
with the <function>list</function> and <function>each</function>
functions to achieve the same effect. See the documentation for
these functions for an example.
</para>
<para>
A foreach statement has been added to PHP4. There are two supported
syteaxes:</para>
</sect1>
<sect1 id="control-structures.foreach">
<title><literal>foreach</literal></title>
<para>
PHP4 (not PHP3) includes a <literal>foreach</literal> construct,
much like perl and some other languages. This simply gives an easy
way to iterate over arrays. There are two syntaxes; the second is
a minor but useful extension of the first:
<informalexample>
<programlisting>
foreach(array_expression as $value) statement
foreach(array_expression as $key => $value) statement
</programlisting>
</informalexample>
</para>
<para>
foreach(array_expression as $v): This will loop through array_expression
assigning the value of the array at the current position to $v, and then
advances the postion by one. See examples 1 and 2 below.</para>
<simpara>
The first form loops over the array given by
<literal>array_expression</literal>. On each loop, the value of
the current element is assigned to <literal>$value</literal> and
the internal array pointer is advanced by one (so on the next
loop, you'll be looking at the next element).
</simpara>
<para>
foreach(array_expression as $k => $v): This will loop through
array_expression assigning the key of the array at the current position
to $k and the value of the array at the current position to $v, and then
advances the postion by one. See example 3 below.</para>
<simpara>
The second form does the same thing, except that the current
element's key will be assigned to the variable
<literal>$key</literal> on each loop.
</simpara>
<informalexample>
<programlisting>
<simpara>
When <literal>foreach</literal> first starts executing, the
internal array pointer is automatically reset to the first element
of the array. This means that you do not need to call
<function>reset</function> before a <literal>foreach</literal>
loop.
</simpara>
<para>
You may have noticed that the following are functionally
identical:
<informalexample>
<programlisting>
reset( $arr );
while( list( , $value ) = each( $arr ) ) {
echo "Value: $value&lt;br&gt;\n";
}
foreach( $arr as $value ) {
echo "Value: $value&lt;br&gt;\n";
}
</programlisting>
</informalexample>
The following are also functionally identical:
<informalexample>
<programlisting>
reset( $arr );
while( list( $key, $value ) = each( $arr ) ) {
echo "Key: $key; Value: $value&lt;br&gt;\n";
}
foreach( $arr as $key => $value ) {
echo "Key: $key; Value: $value&lt;br&gt;\n";
}
</programlisting>
</informalexample>
</para>
<para>
Some more examples to demonstrate usages:
<informalexample>
<programlisting>
/* foreach example 1: value only */
$a = array(1, 2, 3, 17);
foreach($a as $v)
{
print "Current value of \$a: $v.\n";
foreach($a as $v) {
print "Current value of \$a: $v.\n";
}
/* foreach example 2: value (with key printed for illustration) */
@ -449,29 +510,27 @@ $a = array(1, 2, 3, 17);
$i = 0; /* for illustrative purposes only */
foreach($a as $v)
{
print "\$a[$i] => $k.\n";
foreach($a as $v) {
print "\$a[$i] => $k.\n";
}
/* foreach example 3: key and value */
$a = array(
"one" => 1,
"two" => 2,
"three" => 3,
"seventeen" => 17
);
$a = array("one" => 1,
"two" => 2,
"three" => 3,
"seventeen" => 17);
foreach($a as $k => $v)
{
print "\$a[$k] => $v.\n";
foreach($a as $k => $v) {
print "\$a[$k] => $v.\n";
}
</programlisting>
</informalexample>
</para>
</programlisting>
</informalexample>
</sect1>
</sect1>
<sect1 id="control-structures.break">
@ -482,13 +541,13 @@ print "\$a[$k] => $v.\n";
<informalexample>
<programlisting>
$i = 0;
while ($i < 10) {
if ($arr[$i] == "stop") {
break;
}
$i++;
}
$i = 0;
while ($i < 10) {
if ($arr[$i] == "stop") {
break;
}
$i++;
}
</programlisting>
</informalexample></para></sect1>