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Source of: /manual/en/language.operators.precedence.php

<?php
include_once $_SERVER['DOCUMENT_ROOT'] . '/include/shared-manual.inc';
$TOC = array();
$PARENTS = array();
include_once dirname(__FILE__) ."/toc/language.operators.inc";
$setup = array (
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    0 => 'index.php',
    1 => 'PHP Manual',
  ),
  'head' =>
  array (
    0 => 'UTF-8',
    1 => 'en',
  ),
  'this' =>
  array (
    0 => 'language.operators.precedence.php',
    1 => 'Operator Precedence',
  ),
  'up' =>
  array (
    0 => 'language.operators.php',
    1 => 'Operators',
  ),
  'prev' =>
  array (
    0 => 'language.operators.php',
    1 => 'Operators',
  ),
  'next' =>
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    0 => 'language.operators.arithmetic.php',
    1 => 'Arithmetic Operators',
  ),
);
$setup["toc"] = $TOC;
$setup["parents"] = $PARENTS;
manual_setup($setup);

manual_header();
?>
<div id="language.operators.precedence" class="sect1">
   <h2 class="title">Operator Precedence</h2>
   <p class="para">
    The precedence of an operator specifies how &quot;tightly&quot; it binds two
    expressions together. For example, in the expression <i>1 +
    5 * 3</i>, the answer is <i>16</i> and not
    <i>18</i> because the multiplication (&quot;*&quot;) operator
    has a higher precedence than the addition (&quot;+&quot;) operator.
    Parentheses may be used to force precedence, if necessary. For
    instance: <i>(1 + 5) * 3</i> evaluates to
    <i>18</i>. If operator precedence is equal, left to right
    associativity is used.
   </p>
   <p class="para">
    The following table lists the precedence of operators with the
    highest-precedence operators listed at the top of the table. Operators
    on the same line have equal precedence, in which case their
    associativity decides which order to evaluate them in.
    </p><table class="doctable table">
     <caption><b>Operator Precedence</b></caption>
    
      <thead valign="middle">
       <tr valign="middle">
        <th>Associativity</th>
        <th>Operators</th>
        <th>Additional Information</th>
       </tr>

      </thead>

      <tbody valign="middle" class="tbody">
       <tr valign="middle">
        <td align="left">non-associative</td>
        <td align="left">clone new</td>
        <td align="left"><a href="language.oop5.cloning.php" class="link">clone</a> and <a href="language.oop5.basic.php#language.oop5.basic.new" class="link">new</a></td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">[</td>
        <td align="left"><a href="function.array.php" class="function">array()</a></td>
       </tr>

       <tr valign="middle">
        <td align="left">non-associative</td>
        <td align="left">++ --</td>
        <td align="left">
         <a href="language.operators.increment.php" class="link">increment/decrement</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">right</td>
        <td align="left">~ - (int) (float) (string) (array) (object) (bool) @</td>
        <td align="left">
         <a href="language.types.php" class="link">types</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">non-associative</td>
        <td align="left">instanceof</td>
        <td align="left">
         <a href="language.types.php" class="link">types</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">right</td>
        <td align="left">!</td>
        <td align="left">
         <a href="language.operators.logical.php" class="link">logical</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">* / %</td>
        <td align="left">
         <a href="language.operators.arithmetic.php" class="link">arithmetic</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">+ - .</td>
        <td align="left">
         <a href="language.operators.arithmetic.php" class="link">arithmetic</a> and
         <a href="language.operators.string.php" class="link">string</a></td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">&lt;&lt; &gt;&gt;</td>
        <td align="left">
         <a href="language.operators.bitwise.php" class="link">bitwise</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">non-associative</td>
        <td align="left">&lt; &lt;= &gt; &gt;= &lt;&gt;</td>
        <td align="left">
         <a href="language.operators.comparison.php" class="link">comparison</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">non-associative</td>
        <td align="left">== != === !==</td>
        <td align="left">
         <a href="language.operators.comparison.php" class="link">comparison</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">&amp;</td>
        <td align="left">
         <a href="language.operators.bitwise.php" class="link">bitwise</a> and
         <a href="language.references.php" class="link">references</a></td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">^</td>
        <td align="left">
         <a href="language.operators.bitwise.php" class="link">bitwise</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">|</td>
        <td align="left">
         <a href="language.operators.bitwise.php" class="link">bitwise</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">&amp;&amp;</td>
        <td align="left">
         <a href="language.operators.logical.php" class="link">logical</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">||</td>
        <td align="left">
         <a href="language.operators.logical.php" class="link">logical</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">? :</td>
        <td align="left">
         <a href="language.operators.comparison.php#language.operators.comparison.ternary" class="link">ternary</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">right</td>
        <td align="left">
         = += -= *= /= .= %= &amp;= |= ^= &lt;&lt;= &gt;&gt;=
        </td>
        <td align="left">
         <a href="language.operators.assignment.php" class="link">assignment</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">and</td>
        <td align="left">
         <a href="language.operators.logical.php" class="link">logical</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">xor</td>
        <td align="left">
         <a href="language.operators.logical.php" class="link">logical</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">or</td>
        <td align="left">
         <a href="language.operators.logical.php" class="link">logical</a>
        </td>
       </tr>

       <tr valign="middle">
        <td align="left">left</td>
        <td align="left">,</td>
        <td align="left">many uses</td>
       </tr>

      </tbody>
    
    </table>
<p>
   </p>
   <p class="para">
    Left associativity means that the expression is evaluated from left to right,
    right associativity means the opposite.
    </p><div class="example">
     <p><b>Example #1 Associativity</b></p>
     <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$a&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">3&nbsp;</span><span style="color: #007700">*&nbsp;</span><span style="color: #0000BB">3&nbsp;</span><span style="color: #007700">%&nbsp;</span><span style="color: #0000BB">5</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;(3&nbsp;*&nbsp;3)&nbsp;%&nbsp;5&nbsp;=&nbsp;4<br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">true&nbsp;</span><span style="color: #007700">?&nbsp;</span><span style="color: #0000BB">0&nbsp;</span><span style="color: #007700">:&nbsp;</span><span style="color: #0000BB">true&nbsp;</span><span style="color: #007700">?&nbsp;</span><span style="color: #0000BB">1&nbsp;</span><span style="color: #007700">:&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;(true&nbsp;?&nbsp;0&nbsp;:&nbsp;true)&nbsp;?&nbsp;1&nbsp;:&nbsp;2&nbsp;=&nbsp;2<br /><br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$b&nbsp;</span><span style="color: #007700">+=&nbsp;</span><span style="color: #0000BB">3</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;$a&nbsp;=&nbsp;($b&nbsp;+=&nbsp;3)&nbsp;-&gt;&nbsp;$a&nbsp;=&nbsp;5,&nbsp;$b&nbsp;=&nbsp;5<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

    </div><p>
    Use parentheses to increase readability of the code.
   </p>
   <blockquote><p><b class="note">Note</b>:
   
     Although <i>=</i> has a lower precedence than
     most other operators, PHP will still allow expressions
     similar to the following: <i>if (!$a = foo())</i>,
     in which case the return value of <i>foo()</i> is
     put into <var class="varname">$a</var>.
    <br />
   </p></blockquote>
  </div><?php manual_footer(); ?>
 
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