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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>PHP Reference</title>
<meta name="author" content="Ben Thornton">
<link rel="stylesheet" type="text/css" href="styles/style.css">
</head>
<body class="ample" id="phpref">
<h1>PHP Reference</h1>
<ul class="skip">
<li><a href="#toc" accesskey="2">Table of Contents</a></li>
<li><a href="/~bthorn01/index.php" accesskey="1">Home Page</a></li>
<li><a href="colophon.php#access" accesskey="0">Accessibility Statement</a></li>
</ul>
<p><dfn>PHP is a server-side programming language developed specifically
for the Web. It stands for "PHP: Hypertext Preprocessor."</dfn></p>
<p>These are my notes from <cite>Core PHP Programming, 3rd ed.</cite> by
Leon Atkinson and Zeev Suraski. The entire book is <a
href="http://safari.phptr.com/JVXSL.asp?xmlid=0-13-089398-6/d1e1723">available
online</a> (first fortnight free).</p>
<p class="related">See also:
<a href="http://www.php.net/">PHP.net</a>,
<a href="http://zend.com/">Zend.com</a>,
<a href="http://www.w3schools.com/">W3 Schools</a>
</p>
<hr><h2 id="toc">Table of Contents</h2>
<h3 id="toc-brief">Brief</h3><ol>
<!--
<li><a href="#toc">Table of Contents</a></li>
-->
<li><a href="#syntax">Syntax</a></li>
<li><a href="#operators">Operators</a></li>
<!--
<li><a href="#statements">Control Statements</a></li>
-->
<li><a href="#glossary">Glossary</a></li>
</ol>
<h3 id="toc-complete">Complete</h3><ol>
<!--
<li><a href="#toc">Table of Contents</a></li><ol>
<li><a href="#toc-brief">Brief</a></li>
<li><a href="#toc-complete">Complete</a></li>
</ol></li>
-->
<li><a href="#syntax">Syntax</a><ol>
<li><a href="#phptags">PHP Tags</a></li>
<li><a href="#grammar">Grammar</a></li>
<li><a href="#quotes">Quoting Strings</a></li>
<li><a href="#escape">Escape Sequences</a></li>
<li><a href="#variables">Variables</a></li>
<li><a href="#constants">Constants</a></li>
<li><a href="#arrays">Arrays</a></li>
<li><a href="#functions">Functions</a></li>
<li><a href="#classes">Classes</a></li>
<li><a href="#objects">Objects</a></li>
</ol></li>
<li><a href="#operators">Operators</a><ol>
<li><a href="#arithmetic">Arithmetic Operators</a></li>
<li><a href="#assignment">Assignment Operators</a></li>
<li><a href="#relational">Relational Operators</a></li>
<li><a href="#logical">Logical Operators</a></li>
<li><a href="#bitwise">Bitwise Operators</a></li>
<li><a href="#casting">Casting Operators</a></li>
<li><a href="#miscellaneous">Miscellaneous Operators</a></li>
</ol></li>
<!--
<li><a href="#statements">Control Statements</a></li>
-->
<li><a href="#glossary">Glossary</a></li>
</ol>
<hr><h2 id="syntax">Syntax</h2>
<h3 id="phptags">PHP Tags</h3>
<p>PHP scripts happily coexist with HTML in the same file. The way we
distinguish between PHP and HTML code is by enclosing the script between
<code><?php</code> and <code>?></code> tags. Technically, you can
get away with leaving out the <code>php</code>, but XML gets confused
without it, so it's a good idea for forward-compatibility. See
<a href="http://www.php.net/manual/en/language.basic-syntax.php#language.basic-syntax.phpmode">Escaping from HTML</a>
in the online manual, or pp. 1033-4 in the text for a complete
description of PHP tags.</p>
<h3 id="grammar">Grammar</h3>
<p>PHP scripts generally follow the same grammatical rules as C, C++,
and Java.</p><ul>
<li>PHP is case sensitive.</li>
<li>PHP does not care about whitespace.</li>
<li>Each statement must end with a semicolon.</li>
<li>Blocks of code (such as functions, classes, or multi-line control
statements) must be enclosed with curly
braces.</li> <li>Strings and characters must be quoted.</li>
</ul>
<h3 id="quotes">Quoting Strings</h3>
<p>Single-quotes interpret everything inside them literally, with two
exceptions: the escape sequences <code>\'</code> and <code>\\</code>
(interpreted as a single-quote and a backslash, respectively). Double
quotes support several more escape sequences, and <a
href="#interpolate">interpolate</a> variables too.</p>
<p class="related">See also:
<a href="http://us4.php.net/manual/en/ref.info.php#ini.magic-quotes-gpc">
<code>magic_quotes_gpc</code></a>,
<a href="http://us4.php.net/manual/en/ref.info.php#ini.magic-quotes-runtime">
<code>magic_quotes_runtime</code></a>,
<a href="http://us4.php.net/manual/en/function.get-magic-quotes-gpc.php">
<code>get_magic_quotes_gpc()</code></a>,
<a href="http://us4.php.net/manual/en/function.get-magic-quotes-runtime.php">
<code>get_magic_quotes_runtime()</code></a>,
<a href="http://us4.php.net/manual/en/function.set-magic-quotes-gpc.php">
<code>set_magic_quotes_gpc()</code></a>,
<a href="http://us4.php.net/manual/en/function.set-magic-quotes-runtime.php">
<code>set_magic_quotes_runtime()</code></a>,
<a href="http://us4.php.net/manual/en/function.addslashes.php">
<code>addslashes()</code></a>,
<a href="http://us4.php.net/manual/en/function.stripslashes.php">
<code>stripslashes()</code></a>
</p>
<table id="escape" cellspacing="0"><tr>
<th>Escape Sequence</th>
<th>Description</th>
<th><a href="#interpolate">Interpolated</a> when inside:</th>
</tr><tr>
<td><code>\\</code></td>
<td class="desc">Backslash</td>
<td class="desc">Single or Double Quotes</td>
</tr><tr>
<td><code>\'</code></td>
<td class="desc">Single Quote</td>
<td class="desc">Single Quotes only</td>
</tr><tr>
<td><code>\"</code></td>
<td class="desc">Double Quote</td>
<td class="desc" rowspan="6">Double Quotes only</td>
</tr><tr>
<td><code>\$</code></td>
<td class="desc">Dollar Sign</td>
</tr><tr>
<td><code>\n</code></td>
<td class="desc">Newline</td>
</tr><tr>
<td><code>\r</code></td>
<td class="desc">Carriage Return</td>
</tr><tr>
<td><code>\t</code></td>
<td class="desc">Horizontal Tab</td>
</tr><tr>
<td><code>\x00 - \xFF</code></td>
<td class="desc">Hex Character</td>
</tr></table>
<h3 id="variables">Variables</h3>
<p>Variable names must begin with a dollar sign (e.g.
<code>$variableName</code>). They should begin with a lowercase letter
and delimit multiple words with capitals. They cannot begin with a
number. Hyphens are a bad idea, but underscores are okay. Those beginning
with an underscore have special meaning (sort of like keywords).</p>
<p>When assigning a value to a variable, the value to be assigned always
goes to the right of the assignment operator (e.g. <code>$foo =
2 + 2;</code>).
<h3 id="constants">Constants</h3>
<p>The <code>define()</code> function declares constants. You should name
constants using all capital letters. Once declared, a constant cannot be
modified.</p>
<h3 id="arrays">Arrays</h3>
<p>Arrays are just collections of variables. They (like the various data
types) need not be explicitly declared. They can be, however, by using the
<code>array()</code> function.</p>
<p class="related">See also:
<a href="http://us4.php.net/manual/en/control-structures.foreach.php">
<code>foreach</code></a>,
<a href="http://us4.php.net/manual/en/function.count.php">
<code>count()</code></a>,
<a href="http://us4.php.net/manual/en/function.array-pop.php">
<code>array_pop()</code></a>,
<a href="http://us4.php.net/manual/en/function.array-push.php">
<code>array_push()</code></a>,
<a href="http://us4.php.net/manual/en/ref.array.php">
<code>other array functions</code></a>
</p>
<h3 id="functions">Functions</h3>
<p>The keyword <code>function</code> defines functions. Like variables,
the first letter of a function should not be capitalized. A function
may receive zero or more arguments, which must be declared inside the
parentheses as variables. Functions may be overloaded.</p>
<blockquote><pre>
<code><strong>function</strong> <span
title="Function Name">doSomething</span>(<span
title="Argument">$withThis</span>) {
<em>expressions go here</em>
}</code></pre></blockquote>
<h3 id="classes">Classes</h3>
<p>Define classes using the keyword <code>class</code>. The first letter
of a classname should be capitalized. PHP supports single-inheritance.
This means that classes can extend one another, such that each child may
only have a single parent. The keyword <code>extends</code> does what it
says it does.</p>
<blockquote><pre>
<code><strong>class</strong> Child <strong>extends</strong> Parent {
<em>methods and properties go here</em>
}</code></pre></blockquote>
<p>Classes contain methods and properties. Page 104 says it best:</p>
<blockquote><p>From an abstract perspective, methods are things an
object does, and properties are characteristics of the object. From a
programming perspective, methods are functions and properties are
variables.</p></blockquote>
<h3 id="objects">Objects</h3>
<p>Objects are instances of classes. Think of a class as a template,
and an object as an end product. One class may produce many objects,
all of which will behave similarly. You may create new objects by
using the <code>new</code> keyword. It is customary to store new
objects inside variables.</p>
<blockquote><pre>
<code>$thing = <strong>new</strong> Doodad(<em>"red", "shiny"</em>);</code>
</pre></blockquote>
<p>The idea is that objects pass objects back and forth between other
objects, sort of like functions pass variables back and forth. However,
objects can do and be things that variables cannot. Objects also play
nicely with foreign objects.</p>
<hr><h2 id="operators">Operators</h2>
<p>Operators manipulate data. The data being manipulated are called
operands. Unary operators work with one operand, binary operators
work with two. There is only one ternary operator.
<h3 id="arithmetic">Arithmetic Operators</h3>
<table cellspacing="0"
summary="Lists and describes PHP's arithmetic operators, with examples."><tr>
<th>Operator</th>
<th>Purpose</th>
<th>Example</th>
<th>Result</th>
</tr><tr>
<td><code>+</code></td>
<td class="desc">Addition<br>Explicit positive sign</td>
<td><code>12 + 1</code></td>
<td><code>13</code></td>
</tr><tr>
<td><code>-</code></td>
<td class="desc">Subtraction<br>Negation</td>
<td><code>9 - 12</code></td>
<td><code>-3</code></td>
</tr><tr>
<td><code>*</code></td>
<td class="desc">Multiplication</td>
<td><code>3 * 4</code></td>
<td><code>12</code></td>
</tr><tr>
<td><code>/</code></td>
<td class="desc">Division</td>
<td><code>6 / 2</code></td>
<td><code>3</code></td>
</tr><tr>
<td><code>%</code></td>
<td class="desc">Modulo division<br>(remainder)</td>
<td><code>5 % 2</code></td>
<td><code>1</code></td>
</tr><tr>
<td><code>++</code></td>
<td class="desc">Increment</td>
<td><code>7++</code></td>
<td><code>8</code></td>
</tr><tr>
<td><code>--</code></td>
<td class="desc">Decrement</td>
<td><code>7--</code></td>
<td><code>6</code></td>
</tr></table>
<p>Beware of the distinction between post-increment (<code>$value++</code>)
and pre-increment (<code>++$value</code>). Same goes for the decrement
operator.</p>
<h3 id="assignment">Assignment Operators</h3>
<table cellspacing="0" summary="Lists PHP's assignment operators."><tr>
<th>Operator</th>
<th>Purpose</th>
<th>Usage</th>
</tr><tr>
<td><code>=</code></td>
<td class="desc">Assign right to left</td>
<td><code>$a = 13</code></td>
</tr><tr>
<td><code>+=</code></td>
<td class="desc">Add right to left</td>
<td><code>$a += 3</code></td>
</tr><tr>
<td><code>-=</code></td>
<td class="desc">Subtract right from left</td>
<td><code>$a -= 7</code></td>
</tr><tr>
<td><code>*=</code></td>
<td class="desc">Multiply left by right</td>
<td><code>$a *= 2</code></td>
</tr><tr>
<td><code>\=</code></td>
<td class="desc">Divide left by right</td>
<td><code>$a \= 5</code></td>
</tr><tr>
<td><code>%=</code></td>
<td class="desc">Divide left by right,<br>set left to remainder</td>
<td><code>$a %= 21</code></td>
</tr><tr>
<td><code>&=</code></td>
<td class="desc">Compute bitwise-AND,<br>set left to result</td>
<td><code>$a &= $b</code></td>
</tr><tr>
<td><code>|=</code></td>
<td class="desc">Compute bitwise-OR,<br>set left to result</td>
<td><code>$a |= $b</code></td>
</tr><tr>
<td><code>^=</code></td>
<td class="desc">Compute bitwise-XOR,<br>set left to result</td>
<td><code>$a ^= $b</code></td>
</tr><tr>
<td><code>.=</code></td>
<td class="desc">Concatenate values</td>
<td><code>$a .= $b</code></td>
</tr></table>
<p>Using assignment operators to shorten equivalent mathematical
expressions actually produces more efficient code, as PHP only has to
call a variable once rather than twice.</p>
<h3 id="relational">Relational Operators</h3>
<table cellspacing="0" summary="Lists PHP's relational operators."><tr>
<th>Operator</th>
<th>Purpose</th>
<th>Usage</th>
</tr><tr>
<td><code><</code></td>
<td class="desc">Is less than</td>
<td><code>$a < 12</code></td>
</tr><tr>
<td><code>></code></td>
<td class="desc">Is greater than</td>
<td><code>$a $gt; 3</code></td>
</tr><tr>
<td><code><=</code></td>
<td class="desc">Is less than or equal to</td>
<td><code>$a <= $b</code></td>
</tr><tr>
<td><code>>=</code></td>
<td class="desc">Is greater than or equal to</td>
<td><code>$a $gt;= 9</code></td>
</tr><tr>
<td><code>==</code></td>
<td class="desc">Is equal to</td>
<td><code>$a == 1</code></td>
</tr><tr>
<td><code>===</code></td>
<td class="desc">Is identical to</td>
<td><code>$a === TRUE</code></td>
</tr><tr>
<td><code>!=</code></td>
<td class="desc">Is not equal to</td>
<td><code>$a != 1</code></td>
</tr><tr>
<td><code>!==</code></td>
<td class="desc">Is not identical to</td>
<td><code>$a !== NULL</code></td>
</tr></table>
<h3 id="logical">Logical Operators</h3>
<table cellspacing="0" summary="Lists PHP's logical operators."><tr>
<th>Operator</th>
<th>Purpose</th>
<th>Usage</th>
</tr><tr>
<td><code>AND</code></td>
<td class="desc">Logical and</td>
<td><code>$a AND $b</code></td>
</tr><tr>
<td><code>&&</code></td>
<td class="desc">Logical and</td>
<td><code>$a && $b</code></td>
</tr><tr>
<td><code>OR</code></td>
<td class="desc">Logical or</td>
<td><code>$a OR $b</code></td>
</tr><tr>
<td><code>||</code></td>
<td class="desc">Logical or</td>
<td><code>$a || $b</code></td>
</tr><tr>
<td><code>XOR</code></td>
<td class="desc">Exclusive or</td>
<td><code>$a XOR $b</code></td>
</tr><tr>
<td><code>!</code></td>
<td class="desc">Logical not</td>
<td><code>! $a</code></td>
</tr></table>
<!--
<h4>Truth Table for Logical Operators</h4>
<table cellspacing="0"><tr>
<th><code>p</code></th>
<th><code>q</code></th>
</tr><tr>
<td><code>FALSE</code></td>
<td><code>FALSE</code></td>
</tr><tr>
<td><code>FALSE</code></td>
<td><code>TRUE</code></td>
</tr><tr>
<td><code>TRUE</code></td>
<td><code>FALSE</code></td>
</tr><tr>
<td><code>TRUE</code></td>
<td><code>TRUE</code></td>
</tr></table>
<table cellspacing="0"><tr>
<th><code>p AND q</code></th>
<th><code>p OR q</code></th>
<th><code>p XOR q</code></th>
<th><code>!p</code></th>
</tr><tr>
<td><code>FALSE</code></td>
<td><code>FALSE</code></td>
<td><code>FALSE</code></td>
<td><code>TRUE</code></td>
</tr><tr>
<td><code>FALSE</code></td>
<td><code>TRUE</code></td>
<td><code>TRUE</code></td>
<td><code>TRUE</code></td>
</tr><tr>
<td><code>FALSE</code></td>
<td><code>TRUE</code></td>
<td><code>TRUE</code></td>
<td><code>FALSE</code></td>
</tr><tr>
<td><code>TRUE</code></td>
<td><code>TRUE</code></td>
<td><code>FALSE</code></td>
<td><code>FALSE</code></td>
</tr></table>
-->
<h3 id="bitwise">Bitwise Operators</h3>
<!-- To do:
Use binary examples (e.g. 1010) with a results column, instead of
using meaningless variables. How does one specify numbers in bases
other than ten?
-->
<table cellspacing="0" summary="Lists PHP's bitwise operators."><tr>
<th>Operator</th>
<th>Purpose</th>
<th>Usage</th>
</tr><tr>
<td><code>&</code></td>
<td class="desc">Logical and</td>
<td><code>$a & $b</code></td>
</tr><tr>
<td><code>|</code></td>
<td class="desc">Logical or</td>
<td><code>$a | $b</code></td>
</tr><tr>
<td><code>^</code></td>
<td class="desc">Exclusive or</td>
<td><code>$a ^ $b</code></td>
</tr><tr>
<td><code>~</code></td>
<td class="desc">Logical not,<br>or one's complement</td>
<td><code>~$a</code></td>
</tr><tr>
<td><code>>></code></td>
<td class="desc">Shift bits to the right</td>
<td><code>$a >> $b</code></td>
</tr><tr>
<td><code><<</code></td>
<td class="desc">Shift bits to the left</td>
<td><code>$a << $b</code></td>
</tr></table>
<h3 id="casting">Casting Operators</h3>
<table cellspacing="0" summary="Lists PHP's casting operators."><tr>
<th>Operator</th>
<th>Purpose</th>
<th>Usage</th>
</tr><tr>
<td><code>(int)<br>(integer)</code></td>
<td class="desc">Integer cast</td>
<td><code>(integer)$i</code></td>
</tr><tr>
<td><code>(float)<br>(double)<br>(real)</code></td>
<td class="desc">Floating-point cast</td>
<td><code>(float)$f</code></td>
</tr><tr>
<td><code>(string)</code></td>
<td class="desc">String cast</td>
<td><code>(string)$s</code></td>
</tr><tr>
<td><code>(bool)<br>(boolean)</code></td>
<td class="desc">Boolean cast</td>
<td><code>(bool)$b</code></td>
</tr><tr>
<td><code>(array)</code></td>
<td class="desc">Array cast</td>
<td><code>(array)$a</code></td>
</tr><tr>
<td><code>(object)</code></td>
<td class="desc">Object cast</td>
<td><code>(object)$o</code></td>
</tr></table>
<h3 id="miscellaneous">Miscellaneous Operators</h3>
<table cellspacing="0" summary="Lists PHP's miscellaneous operators."><tr>
<th>Operator</th>
<th>Purpose</th>
<th>Usage</th>
</tr><tr>
<td><code>.</code></td>
<td class="desc">Concatenate</td>
<td><code>$a . $b</code></td>
</tr><tr>
<td><code>$</code></td>
<td class="desc">Indirect Reference</td>
<td><code>$$a</code></td>
</tr><tr>
<td><code>@</code></td>
<td class="desc">Silence (suppress error messages)</td>
<td><code>@($a/$b)</code></td>
</tr><tr>
<td><code>? :</code></td>
<td class="desc">Ternary conditional expression</td>
<td><code>($a === TRUE) ? "true" : "false"</code></td>
</tr><tr>
<td><code>{}</code></td>
<td class="desc">Embed variable in a string</td>
<td><code>a is {$a}</code></td>
</tr><tr>
<td><code>` `</code></td>
<td class="desc">Execute shell command</td>
<td><code>`ll -A`</code></td>
</tr><tr>
<td><code>=></code></td>
<td class="desc">Assign array index</td>
<td><code>array(0=>'Sunday')</code></td>
</tr><tr>
<td><code>-></code></td>
<td class="desc">Reference an object</td>
<td><code>$o->method()</code></td>
</tr><tr>
<td><code>::</code></td>
<td class="desc">Reference a class</td>
<td><code>Widgets::method()</code></td>
</tr><tr>
<!-- Seems like a keyword to me. Is their a meaningful difference
between keywords and operators, or is it just their constitution? -->
<td><code>instanceof</code></td>
<td class="desc">Test if an object is an instance of a class</td>
<td><code>$w instanceof Widgets</code></td>
</tr></table>
<!--
<hr><h2 id="statements">Control Statements</h2>
-->
<hr><h2 id="glossary">Glossary</h2><dl>
<dt id="interpolate">Interpolate</dt>
<dd><i>v.</i> to infer meaning, and alter information (perhaps
erroneously).</dd>
<dd>Commonly used within computer science as an antonym to "interpret"
(read "interpret <em>literally</em>"). That is, a variable name or an
escape sequence will be recognized and replaced by its associated value.
The word "extrapolate" is actually more accurate, but rarely if ever
used.</dd>
<!--
<dt></dt>
<dd></dd>
-->
</dl><!-- End glossary -->
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