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php-manual-ro-20051028-1.noarch.rpm

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>Manual PHP</TH
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><A
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>Înapoi</A
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><TD
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>Cap. 11. Control Structures</TD
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><VAR
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>for</VAR
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></H1
><P
>&#13;    <VAR
CLASS="literal"
>for</VAR
> loops are the most complex loops in PHP.
    They behave like their C counterparts.  The syntax of a
    <VAR
CLASS="literal"
>for</VAR
> loop is:
    <DIV
CLASS="informalexample"
><P
></P
><A
NAME="AEN2525"
></A
><TABLE
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><TR
><TD
><PRE
CLASS="programlisting"
>for (expr1; expr2; expr3) statement</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
   </P
><P
>&#13;    The first expression (<VAR
CLASS="varname"
>expr1</VAR
>) is
    evaluated (executed) once unconditionally at the beginning of the
    loop.
   </P
><P
>&#13;    In the beginning of each iteration,
    <VAR
CLASS="varname"
>expr2</VAR
> is evaluated.  If it evaluates to
    <TT
CLASS="constant"
><B
>TRUE</B
></TT
>, the loop continues and the nested
    statement(s) are executed.  If it evaluates to
    <TT
CLASS="constant"
><B
>FALSE</B
></TT
>, the execution of the loop ends.
   </P
><P
>&#13;    At the end of each iteration, <VAR
CLASS="varname"
>expr3</VAR
> is
    evaluated (executed).
   </P
><P
>&#13;    Each of the expressions can be empty.
    <VAR
CLASS="varname"
>expr2</VAR
> being empty means the loop should
    be run indefinitely (PHP implicitly considers it as
    <TT
CLASS="constant"
><B
>TRUE</B
></TT
>, like C).  This may not be as useless as
    you might think, since often you'd want to end the loop using a
    conditional <A
HREF="control-structures.break.html"
><VAR
CLASS="literal"
>break</VAR
></A
>
    statement instead of using the <VAR
CLASS="literal"
>for</VAR
> truth
    expression.
   </P
><P
>&#13;    Consider the following examples.  All of them display numbers from
    1 to 10:
    <DIV
CLASS="informalexample"
><P
></P
><A
NAME="AEN2542"
></A
><TABLE
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><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br /></font><font color="#FF8000">/* example 1 */<br /><br /></font><font color="#007700">for (</font><font color="#0000BB">$i </font><font color="#007700">= </font><font color="#0000BB">1</font><font color="#007700">; </font><font color="#0000BB">$i </font><font color="#007700">&lt;= </font><font color="#0000BB">10</font><font color="#007700">; </font><font color="#0000BB">$i</font><font color="#007700">++) {<br />&nbsp;&nbsp;&nbsp;&nbsp;echo </font><font color="#0000BB">$i</font><font color="#007700">;<br />}<br /><br /></font><font color="#FF8000">/* example 2 */<br /><br /></font><font color="#007700">for (</font><font color="#0000BB">$i </font><font color="#007700">= </font><font color="#0000BB">1</font><font color="#007700">; ; </font><font color="#0000BB">$i</font><font color="#007700">++) {<br />&nbsp;&nbsp;&nbsp;&nbsp;if (</font><font color="#0000BB">$i </font><font color="#007700">&gt; </font><font color="#0000BB">10</font><font color="#007700">) {<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;echo </font><font color="#0000BB">$i</font><font color="#007700">;<br />}<br /><br /></font><font color="#FF8000">/* example 3 */<br /><br /></font><font color="#0000BB">$i </font><font color="#007700">= </font><font color="#0000BB">1</font><font color="#007700">;<br />for (; ; ) {<br />&nbsp;&nbsp;&nbsp;&nbsp;if (</font><font color="#0000BB">$i </font><font color="#007700">&gt; </font><font color="#0000BB">10</font><font color="#007700">) {<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;echo </font><font color="#0000BB">$i</font><font color="#007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">$i</font><font color="#007700">++;<br />}<br /><br /></font><font color="#FF8000">/* example 4 */<br /><br /></font><font color="#007700">for (</font><font color="#0000BB">$i </font><font color="#007700">= </font><font color="#0000BB">1</font><font color="#007700">; </font><font color="#0000BB">$i </font><font color="#007700">&lt;= </font><font color="#0000BB">10</font><font color="#007700">; print </font><font color="#0000BB">$i</font><font color="#007700">, </font><font color="#0000BB">$i</font><font color="#007700">++);<br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
></P
></DIV
>
   </P
><P
>&#13;    Of course, the first example appears to be the nicest one (or
    perhaps the fourth), but you may find that being able to use empty
    expressions in <VAR
CLASS="literal"
>for</VAR
> loops comes in handy in many
    occasions.
   </P
><P
>&#13;    PHP also supports the alternate "colon syntax" for
    <VAR
CLASS="literal"
>for</VAR
> loops.
    <DIV
CLASS="informalexample"
><P
></P
><A
NAME="AEN2548"
></A
><TABLE
BORDER="0"
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><TR
><TD
><PRE
CLASS="programlisting"
>for (expr1; expr2; expr3): statement; ...; endfor;</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
   </P
><P
>&#13;    Other languages have a <VAR
CLASS="literal"
>foreach</VAR
> statement to
    traverse an array or hash. PHP 3 has no such construct; PHP 4 does
    (see <A
HREF="control-structures.foreach.html"
>foreach</A
>). In PHP 3, you
    can combine <A
HREF="control-structures.while.html"
>while</A
>
    with the <A
HREF="function.list.html"
><B
CLASS="function"
>list()</B
></A
> and <A
HREF="function.each.html"
><B
CLASS="function"
>each()</B
></A
>
    functions to achieve the same effect. See the documentation for
    these functions for an example.
   </P
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