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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<sect1 xml:id="control-structures.while" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title>while</title>
<?phpdoc print-version-for="while"?>
<para>
<literal>while</literal> loops are the simplest type of loop in
PHP. They behave just like their C counterparts. The basic form
of a <literal>while</literal> statement is:
<informalexample>
<programlisting>
<![CDATA[
while (expr)
statement
]]>
</programlisting>
</informalexample>
</para>
<simpara>
The meaning of a <literal>while</literal> statement is simple. It
tells PHP to execute the nested statement(s) repeatedly, as long
as the <literal>while</literal> expression evaluates to
&true;. The value of the expression is checked
each time at the beginning of the loop, so even if this value
changes during the execution of the nested statement(s), execution
will not stop until the end of the iteration (each time PHP runs
the statements in the loop is one iteration). If the
<literal>while</literal> expression evaluates to
&false; from the very beginning, the nested
statement(s) won't even be run once.
</simpara>
<para>
Like with the <literal>if</literal> statement, you can group
multiple statements within the same <literal>while</literal> loop
by surrounding a group of statements with curly braces, or by
using the alternate syntax:
<informalexample>
<programlisting>
<![CDATA[
while (expr):
statement
...
endwhile;
]]>
</programlisting>
</informalexample>
</para>
<para>
The following examples are identical, and both print the numbers
1 through 10:
<informalexample>
<programlisting role="php">
<![CDATA[
<?php
/* example 1 */
$i = 1;
while ($i <= 10) {
echo $i++; /* the printed value would be
$i before the increment
(post-increment) */
}
/* example 2 */
$i = 1;
while ($i <= 10):
echo $i;
$i++;
endwhile;
?>
]]>
</programlisting>
</informalexample>
</para>
</sect1>
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