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</div><hr /><div id="control-structures.switch" class="sect1">
<h2 class="title"><em>switch</em></h2>
<p class="verinfo">(PHP 4, PHP 5)</p>
<p class="simpara">
The <em>switch</em> statement is similar to a series of
IF statements on the same expression. In many occasions, you may
want to compare the same variable (or expression) with many
different values, and execute a different piece of code depending
on which value it equals to. This is exactly what the
<em>switch</em> statement is for.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
Note that unlike some other languages, the
<a href="control-structures.continue.html" class="link">continue</a> statement
applies to switch and acts similar to <em>break</em>. If you
have a switch inside a loop and wish to continue to the next iteration of
the outer loop, use <em>continue 2</em>.
</span>
</p></blockquote>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Note that switch/case does
<a href="types.comparisons.html#types.comparisions-loose" class="link">loose comparision</a>.
</p>
</p></blockquote>
<p class="para">
The following two examples are two different ways to write the
same thing, one using a series of <em>if</em> and
<em>elseif</em> statements, and the other using the
<em>switch</em> statement:
<div class="example" id="example-135">
<p><strong>Example #1 <em>switch</em> structure</strong></p>
<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">$i </span><span style="color: #007700">== </span><span style="color: #0000BB">0</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"i equals 0"</span><span style="color: #007700">;<br />} elseif (</span><span style="color: #0000BB">$i </span><span style="color: #007700">== </span><span style="color: #0000BB">1</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"i equals 1"</span><span style="color: #007700">;<br />} elseif (</span><span style="color: #0000BB">$i </span><span style="color: #007700">== </span><span style="color: #0000BB">2</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"i equals 2"</span><span style="color: #007700">;<br />}<br /><br />switch (</span><span style="color: #0000BB">$i</span><span style="color: #007700">) {<br /> case </span><span style="color: #0000BB">0</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 0"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #0000BB">1</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 1"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #0000BB">2</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 2"</span><span style="color: #007700">;<br /> break;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-136">
<p><strong>Example #2 <em>switch</em> structure allows usage of strings</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">switch (</span><span style="color: #0000BB">$i</span><span style="color: #007700">) {<br /> case </span><span style="color: #DD0000">"apple"</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i is apple"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #DD0000">"bar"</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i is bar"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #DD0000">"cake"</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i is cake"</span><span style="color: #007700">;<br /> break;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
It is important to understand how the <em>switch</em>
statement is executed in order to avoid mistakes. The
<em>switch</em> statement executes line by line
(actually, statement by statement). In the beginning, no code is
executed. Only when a <em>case</em> statement is found
with a value that matches the value of the
<em>switch</em> expression does PHP begin to execute the
statements. PHP continues to execute the statements until the end
of the <em>switch</em> block, or the first time it sees
a <em>break</em> statement. If you don't write a
<em>break</em> statement at the end of a case's
statement list, PHP will go on executing the statements of the
following case. For example:
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">switch (</span><span style="color: #0000BB">$i</span><span style="color: #007700">) {<br /> case </span><span style="color: #0000BB">0</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 0"</span><span style="color: #007700">;<br /> case </span><span style="color: #0000BB">1</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 1"</span><span style="color: #007700">;<br /> case </span><span style="color: #0000BB">2</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 2"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="simpara">
Here, if <var class="varname"><var class="varname">$i</var></var> is equal to 0, PHP would execute all of the echo
statements! If <var class="varname"><var class="varname">$i</var></var> is equal to 1, PHP would execute the last two
echo statements. You would get the expected behavior ('i equals 2'
would be displayed) only if <var class="varname"><var class="varname">$i</var></var> is equal to 2. Thus,
it is important not to forget <em>break</em> statements
(even though you may want to avoid supplying them on purpose under
certain circumstances).
</p>
<p class="simpara">
In a <em>switch</em> statement, the condition is
evaluated only once and the result is compared to each
<em>case</em> statement. In an <em>elseif</em>
statement, the condition is evaluated again. If your condition is
more complicated than a simple compare and/or is in a tight loop,
a <em>switch</em> may be faster.
</p>
<p class="para">
The statement list for a case can also be empty, which simply
passes control into the statement list for the next case.
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">switch (</span><span style="color: #0000BB">$i</span><span style="color: #007700">) {<br />case </span><span style="color: #0000BB">0</span><span style="color: #007700">:<br />case </span><span style="color: #0000BB">1</span><span style="color: #007700">:<br />case </span><span style="color: #0000BB">2</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i is less than 3 but not negative"</span><span style="color: #007700">;<br /> break;<br />case </span><span style="color: #0000BB">3</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i is 3"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
A special case is the <em>default</em> case. This case matches
anything that wasn't matched by the other cases. For example:
<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">switch (</span><span style="color: #0000BB">$i</span><span style="color: #007700">) {<br /> case </span><span style="color: #0000BB">0</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 0"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #0000BB">1</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 1"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #0000BB">2</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 2"</span><span style="color: #007700">;<br /> break;<br /> default:<br /> echo </span><span style="color: #DD0000">"i is not equal to 0, 1 or 2"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
The <em>case</em> expression may be any expression that
evaluates to a simple type, that is, integer or floating-point
numbers and strings. Arrays or objects cannot be used here unless
they are dereferenced to a simple type.
</p>
<p class="para">
The alternative syntax for control structures is supported with
switches. For more information, see <a href="control-structures.alternative-syntax.html" class="link">Alternative syntax
for control structures</a>.
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">switch (</span><span style="color: #0000BB">$i</span><span style="color: #007700">):<br /> case </span><span style="color: #0000BB">0</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 0"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #0000BB">1</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 1"</span><span style="color: #007700">;<br /> break;<br /> case </span><span style="color: #0000BB">2</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"i equals 2"</span><span style="color: #007700">;<br /> break;<br /> default:<br /> echo </span><span style="color: #DD0000">"i is not equal to 0, 1 or 2"</span><span style="color: #007700">;<br />endswitch;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
It's possible to use a semicolon instead of a colon after a case like:
<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">switch(</span><span style="color: #0000BB">$beer</span><span style="color: #007700">)<br />{<br /> case </span><span style="color: #DD0000">'tuborg'</span><span style="color: #007700">;<br /> case </span><span style="color: #DD0000">'carlsberg'</span><span style="color: #007700">;<br /> case </span><span style="color: #DD0000">'heineken'</span><span style="color: #007700">;<br /> echo </span><span style="color: #DD0000">'Good choice'</span><span style="color: #007700">;<br /> break;<br /> default;<br /> echo </span><span style="color: #DD0000">'Please make a new selection...'</span><span style="color: #007700">;<br /> break;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
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