language.operators.comparison.html

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     <tbody valign="middle" class="tbody">
      <tr valign="middle">
       <td colspan="1" rowspan="1" align="left"><a href="language.types.null.html" class="type null">null</a> or <a href="language.types.string.html" class="type string">string</a></td>
       <td colspan="1" rowspan="1" align="left"><a href="language.types.string.html" class="type string">string</a></td>
       <td colspan="1" rowspan="1" align="left">Convert <b><tt>NULL</tt></b> to &quot;&quot;, numerical or lexical comparison</td>
      </tr>

      <tr valign="middle">
       <td colspan="1" rowspan="1" align="left"><a href="language.types.boolean.html" class="type bool">bool</a> or <a href="language.types.null.html" class="type null">null</a></td>
       <td colspan="1" rowspan="1" align="left">anything</td>
       <td colspan="1" rowspan="1" align="left">Convert to <a href="language.types.boolean.html" class="type bool">bool</a>, <b><tt>FALSE</tt></b> &lt; <b><tt>TRUE</tt></b></td>
      </tr>

      <tr valign="middle">
       <td colspan="1" rowspan="1" align="left"><a href="language.types.object.html" class="type object">object</a></td>
       <td colspan="1" rowspan="1" align="left"><a href="language.types.object.html" class="type object">object</a></td>
       <td colspan="1" rowspan="1" align="left">Built-in classes can define its own comparison, different classes
        are uncomparable, same class - compare properties the same way as
        arrays (PHP 4), PHP 5 has its own <a href="language.oop5.object-comparison.html" class="link">explanation</a>
       </td>
      </tr>

      <tr valign="middle">
       <td colspan="1" rowspan="1" align="left"><a href="language.types.string.html" class="type string">string</a>, <a href="language.types.resource.html" class="type resource">resource</a> or <a href="language.pseudo-types.html#language.types.number" class="type number">number</a></td>
       <td colspan="1" rowspan="1" align="left"><a href="language.types.string.html" class="type string">string</a>, <a href="language.types.resource.html" class="type resource">resource</a> or <a href="language.pseudo-types.html#language.types.number" class="type number">number</a></td>
       <td colspan="1" rowspan="1" align="left">Translate strings and resources to numbers, usual math</td>
      </tr>

      <tr valign="middle">
       <td colspan="1" rowspan="1" align="left"><a href="language.types.array.html" class="type array">array</a></td>
       <td colspan="1" rowspan="1" align="left"><a href="language.types.array.html" class="type array">array</a></td>
       <td colspan="1" rowspan="1" align="left">Array with fewer members is smaller, if key from operand 1 is not
        found in operand 2 then arrays are uncomparable, otherwise - compare
        value by value (see following example)</td>
      </tr>

      <tr valign="middle">
       <td colspan="1" rowspan="1" align="left"><a href="language.types.array.html" class="type array">array</a></td>
       <td colspan="1" rowspan="1" align="left">anything</td>
       <td colspan="1" rowspan="1" align="left"><a href="language.types.array.html" class="type array">array</a> is always greater</td>
      </tr>

      <tr valign="middle">
       <td colspan="1" rowspan="1" align="left"><a href="language.types.object.html" class="type object">object</a></td>
       <td colspan="1" rowspan="1" align="left">anything</td>
       <td colspan="1" rowspan="1" align="left"><a href="language.types.object.html" class="type object">object</a> is always greater</td>
      </tr>

     </tbody>
    </colgroup>

   </table>

   <p class="para">
    <div class="example">
     <p><b>Example #1 Transcription of standard array comparison</b></p>
     <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;Arrays&nbsp;are&nbsp;compared&nbsp;like&nbsp;this&nbsp;with&nbsp;standard&nbsp;comparison&nbsp;operators<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">standard_array_compare</span><span style="color: #007700">(</span><span style="color: #0000BB">$op1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$op2</span><span style="color: #007700">)<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$op1</span><span style="color: #007700">)&nbsp;&lt;&nbsp;</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$op2</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;-</span><span style="color: #0000BB">1</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;$op1&nbsp;&lt;&nbsp;$op2<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">}&nbsp;elseif&nbsp;(</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$op1</span><span style="color: #007700">)&nbsp;&gt;&nbsp;</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$op2</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;$op1&nbsp;&gt;&nbsp;$op2<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">}<br />&nbsp;&nbsp;&nbsp;&nbsp;foreach&nbsp;(</span><span style="color: #0000BB">$op1&nbsp;</span><span style="color: #007700">as&nbsp;</span><span style="color: #0000BB">$key&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">$val</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(!</span><span style="color: #0000BB">array_key_exists</span><span style="color: #007700">(</span><span style="color: #0000BB">$key</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$op2</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span style="color: #0000BB">null</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;uncomparable<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">}&nbsp;elseif&nbsp;(</span><span style="color: #0000BB">$val&nbsp;</span><span style="color: #007700">&lt;&nbsp;</span><span style="color: #0000BB">$op2</span><span style="color: #007700">[</span><span style="color: #0000BB">$key</span><span style="color: #007700">])&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;-</span><span style="color: #0000BB">1</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;elseif&nbsp;(</span><span style="color: #0000BB">$val&nbsp;</span><span style="color: #007700">&gt;&nbsp;</span><span style="color: #0000BB">$op2</span><span style="color: #007700">[</span><span style="color: #0000BB">$key</span><span style="color: #007700">])&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;$op1&nbsp;==&nbsp;$op2<br /></span><span style="color: #007700">}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

    </div> 
   </p>

   <p class="para">
    See also <a href="function.strcasecmp.html" class="function">strcasecmp()</a>,
    <a href="function.strcmp.html" class="function">strcmp()</a>,
    <a href="language.operators.array.html" class="link">Array operators</a>,
    and the manual section on
    <a href="language.types.html" class="link">Types</a>.
   </p>

   <div id="language.operators.comparison.ternary" class="sect2">
    <h3 class="title">Ternary Operator</h3>
    <p class="para">
     Another conditional operator is the &quot;?:&quot; (or ternary) operator.
     <div class="example">
      <p><b>Example #2 Assigning a default value</b></p>
      <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;Example&nbsp;usage&nbsp;for:&nbsp;Ternary&nbsp;Operator<br /></span><span style="color: #0000BB">$action&nbsp;</span><span style="color: #007700">=&nbsp;(empty(</span><span style="color: #0000BB">$_POST</span><span style="color: #007700">[</span><span style="color: #DD0000">'action'</span><span style="color: #007700">]))&nbsp;?&nbsp;</span><span style="color: #DD0000">'default'&nbsp;</span><span style="color: #007700">:&nbsp;</span><span style="color: #0000BB">$_POST</span><span style="color: #007700">[</span><span style="color: #DD0000">'action'</span><span style="color: #007700">];<br /><br /></span><span style="color: #FF8000">//&nbsp;The&nbsp;above&nbsp;is&nbsp;identical&nbsp;to&nbsp;this&nbsp;if/else&nbsp;statement<br /></span><span style="color: #007700">if&nbsp;(empty(</span><span style="color: #0000BB">$_POST</span><span style="color: #007700">[</span><span style="color: #DD0000">'action'</span><span style="color: #007700">]))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$action&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'default'</span><span style="color: #007700">;<br />}&nbsp;else&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$action&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$_POST</span><span style="color: #007700">[</span><span style="color: #DD0000">'action'</span><span style="color: #007700">];<br />}<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
      </div>

     </div> 
     The expression <i>(expr1) ? (expr2) : (expr3)</i>
     evaluates to <span class="replaceable">expr2</span> if
     <span class="replaceable">expr1</span> evaluates to <b><tt>TRUE</tt></b>, and
     <span class="replaceable">expr3</span> if
     <span class="replaceable">expr1</span> evaluates to <b><tt>FALSE</tt></b>.
    </p>
    <blockquote><p><b class="note">Note</b>: 
     <span class="simpara">
      Please note that the ternary operator is a statement, and that it
      doesn&#039;t evaluate to a variable, but to the result of a statement. This
      is important to know if you want to return a variable by reference.
      The statement <i>return $var == 42 ? $a : $b;</i> in a
      return-by-reference function will therefore not work and a warning is
      issued in later PHP versions.
     </span>
    </p></blockquote>
    <blockquote><p><b class="note">Note</b>: 
     
      Is is recommended that you avoid &quot;stacking&quot; ternary expressions. PHP&#039;s
      behaviour when using more than one ternary operator within a single
      statement is non-obvious:
      <div class="example">
       <p><b>Example #3 Non-obvious Ternary Behaviour</b></p>
       <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;on&nbsp;first&nbsp;glance,&nbsp;the&nbsp;following&nbsp;appears&nbsp;to&nbsp;output&nbsp;'true'<br /></span><span style="color: #007700">echo&nbsp;(</span><span style="color: #0000BB">true</span><span style="color: #007700">?</span><span style="color: #DD0000">'true'</span><span style="color: #007700">:</span><span style="color: #0000BB">false</span><span style="color: #007700">?</span><span style="color: #DD0000">'t'</span><span style="color: #007700">:</span><span style="color: #DD0000">'f'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;however,&nbsp;the&nbsp;actual&nbsp;output&nbsp;of&nbsp;the&nbsp;above&nbsp;is&nbsp;'t'<br />//&nbsp;this&nbsp;is&nbsp;because&nbsp;ternary&nbsp;expressions&nbsp;are&nbsp;evaluated&nbsp;from&nbsp;left&nbsp;to&nbsp;right<br /><br />//&nbsp;the&nbsp;following&nbsp;is&nbsp;a&nbsp;more&nbsp;obvious&nbsp;version&nbsp;of&nbsp;the&nbsp;same&nbsp;code&nbsp;as&nbsp;above<br /></span><span style="color: #007700">echo&nbsp;((</span><span style="color: #0000BB">true&nbsp;</span><span style="color: #007700">?&nbsp;</span><span style="color: #DD0000">'true'&nbsp;</span><span style="color: #007700">:&nbsp;</span><span style="color: #DD0000">'false'</span><span style="color: #007700">)&nbsp;?&nbsp;</span><span style="color: #DD0000">'t'&nbsp;</span><span style="color: #007700">:&nbsp;</span><span style="color: #DD0000">'f'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;here,&nbsp;you&nbsp;can&nbsp;see&nbsp;that&nbsp;the&nbsp;first&nbsp;expression&nbsp;is&nbsp;evaluated&nbsp;to&nbsp;'true',&nbsp;which<br />//&nbsp;in&nbsp;turn&nbsp;evaluates&nbsp;to&nbsp;(bool)true,&nbsp;thus&nbsp;returning&nbsp;the&nbsp;true&nbsp;branch&nbsp;of&nbsp;the<br />//&nbsp;second&nbsp;ternary&nbsp;expression.<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
       </div>

      </div>
     <br />
    </p></blockquote>
   </div>

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