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<HTML
><HEAD
><TITLE
>Control Structures</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.57"><LINK
REL="HOME"
TITLE="PHP Manual"
HREF="manual.html"><LINK
REL="UP"
TITLE="Language Reference"
HREF="langref.html"><LINK
REL="PREVIOUS"
TITLE="String Operators"
HREF="language.operators.string.html"><LINK
REL="NEXT"
TITLE="else"
HREF="control-structures.else.html"><META
NAME="HTTP_EQUIV"
CONTENT="text/html; charset=ISO-8859-1"></HEAD
><BODY
CLASS="chapter"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>PHP Manual</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="language.operators.string.html"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="control-structures.else.html"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="chapter"
><H1
><A
NAME="control-structures"
>Chapter 11. Control Structures</A
></H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="control-structures.html#control-structures.if"
><TT
CLASS="literal"
>if</TT
></A
></DT
><DT
><A
HREF="control-structures.else.html"
><TT
CLASS="literal"
>else</TT
></A
></DT
><DT
><A
HREF="control-structures.elseif.html"
><TT
CLASS="literal"
>elseif</TT
></A
></DT
><DT
><A
HREF="control-structures.alternative-syntax.html"
>Alternative syntax for control structures</A
></DT
><DT
><A
HREF="control-structures.while.html"
><TT
CLASS="literal"
>while</TT
></A
></DT
><DT
><A
HREF="control-structures.do.while.html"
><TT
CLASS="literal"
>do..while</TT
></A
></DT
><DT
><A
HREF="control-structures.for.html"
><TT
CLASS="literal"
>for</TT
></A
></DT
><DT
><A
HREF="control-structures.foreach.html"
><TT
CLASS="literal"
>foreach</TT
></A
></DT
><DT
><A
HREF="control-structures.break.html"
><TT
CLASS="literal"
>break</TT
></A
></DT
><DT
><A
HREF="control-structures.continue.html"
><TT
CLASS="literal"
>continue</TT
></A
></DT
><DT
><A
HREF="control-structures.switch.html"
><TT
CLASS="literal"
>switch</TT
></A
></DT
><DT
><A
HREF="function.require.html"
><A
HREF="function.require.html"
><B
CLASS="function"
>require()</B
></A
></A
></DT
><DT
><A
HREF="function.include.html"
><A
HREF="function.include.html"
><B
CLASS="function"
>include()</B
></A
></A
></DT
><DT
><A
HREF="function.require-once.html"
><A
HREF="function.require-once.html"
><B
CLASS="function"
>require_once()</B
></A
></A
></DT
><DT
><A
HREF="function.include-once.html"
><A
HREF="function.include-once.html"
><B
CLASS="function"
>include_once()</B
></A
></A
></DT
></DL
></DIV
><P
> Any PHP script is built out of a series of statements. A statement
can be an assignment, a function call, a loop, a conditional
statement of even a statement that does nothing (an empty
statement). Statements usually end with a semicolon. In addition,
statements can be grouped into a statement-group by encapsulating a
group of statements with curly braces. A statement-group is a
statement by itself as well. The various statement types are
described in this chapter.
</P
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="control-structures.if"
><TT
CLASS="literal"
>if</TT
></A
></H1
><P
> The <TT
CLASS="literal"
>if</TT
> construct is one of the most important
features of many languages, PHP included. It allows for
conditional execution of code fragments. PHP features an
<TT
CLASS="literal"
>if</TT
> structure that is similar to that of C:
<DIV
CLASS="informalexample"
><A
NAME="AEN3298"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
> if (expr)
statement
</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
</P
><P
> As described in the section about expressions, expr is evaluated
to its truth value. If <TT
CLASS="replaceable"
><I
>expr</I
></TT
> evaluates
to <TT
CLASS="literal"
>TRUE</TT
>, PHP will execute statement, and if it
evaluates to <TT
CLASS="literal"
>FALSE</TT
> - it'll ignore it.
</P
><P
> The following example would display <TT
CLASS="computeroutput"
>a is bigger
than b</TT
> if <TT
CLASS="replaceable"
><I
>$a</I
></TT
> is bigger
than <TT
CLASS="replaceable"
><I
>$b</I
></TT
>:
<DIV
CLASS="informalexample"
><A
NAME="AEN3308"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
> if ($a > $b)
print "a is bigger than b";
</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
</P
><P
> Often you'd want to have more than one statement to be executed
conditionally. Of course, there's no need to wrap each statement
with an <TT
CLASS="literal"
>if</TT
> clause. Instead, you can group
several statements into a statement group. For example, this code
would display <TT
CLASS="computeroutput"
>a is bigger than b</TT
>
if <TT
CLASS="replaceable"
><I
>$a</I
></TT
> is bigger than
<TT
CLASS="replaceable"
><I
>$b</I
></TT
>, and would then assign the value of
<TT
CLASS="replaceable"
><I
>$a</I
></TT
> into <TT
CLASS="replaceable"
><I
>$b</I
></TT
>:
<DIV
CLASS="informalexample"
><A
NAME="AEN3317"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
> if ($a > $b) {
print "a is bigger than b";
$b = $a;
}
</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
</P
><P
> If statements can be nested indefinitely within other
<TT
CLASS="literal"
>if</TT
> statements, which provides you with complete
flexibility for conditional execution of the various parts of your
program.
</P
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="language.operators.string.html"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="manual.html"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="control-structures.else.html"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>String Operators</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="langref.html"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><TT
CLASS="literal"
>else</TT
></TD
></TR
></TABLE
></DIV
></BODY
></HTML
>