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<h2 class="title"><em>if</em></h2>
<p class="verinfo">(PHP 4, PHP 5)</p>
<p class="para">
The <em>if</em> construct is one of the most important
features of many languages, PHP included. It allows for
conditional execution of code fragments. PHP features an
<em>if</em> structure that is similar to that of C:
<div class="informalexample">
<div class="example-contents">
<div class="cdata"><pre>
if (expr)
statement
</pre></div>
</div>
</div>
</p>
<p class="simpara">
As described in <a href="language.expressions.html" class="link">the section about
expressions</a>, <span class="replaceable">expression</span> is evaluated to its
Boolean value. If <span class="replaceable">expression</span> evaluates to <strong><code>TRUE</code></strong>,
PHP will execute <span class="replaceable">statement</span>, and if it evaluates
to <strong><code>FALSE</code></strong> - it'll ignore it. More information about what values evaluate
to <strong><code>FALSE</code></strong> can be found in the <a href="language.types.boolean.html#language.types.boolean.casting" class="link">'Converting to boolean'</a>
section.
</p>
<p class="para">
The following example would display <span class="computeroutput">a is bigger
than b</span> if <var class="varname"><var class="varname">$a</var></var> is bigger
than <var class="varname"><var class="varname">$b</var></var>:
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">$a </span><span style="color: #007700">> </span><span style="color: #0000BB">$b</span><span style="color: #007700">)<br /> echo </span><span style="color: #DD0000">"a is bigger than b"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
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 <em>if</em> clause. Instead, you can group
several statements into a statement group. For example, this code
would display <span class="computeroutput">a is bigger than b</span>
if <var class="varname"><var class="varname">$a</var></var> is bigger than
<var class="varname"><var class="varname">$b</var></var>, and would then assign the value of
<var class="varname"><var class="varname">$a</var></var> into <var class="varname"><var class="varname">$b</var></var>:
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">$a </span><span style="color: #007700">> </span><span style="color: #0000BB">$b</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"a is bigger than b"</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$b </span><span style="color: #007700">= </span><span style="color: #0000BB">$a</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="simpara">
<em>If</em> statements can be nested infinitely within other
<em>if</em> statements, which provides you with complete
flexibility for conditional execution of the various parts of your
program.
</p>
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