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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Strings</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="language.types.float.html">Floating point numbers</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.types.array.html">Arrays</a></div> <div class="up"><a href="language.types.html">Types</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="language.types.string" class="sect1"> <h2 class="title">Strings</h2> <p class="para"> A <a href="language.types.string.html" class="type string">string</a> is series of characters. Before PHP 6, a character is the same as a byte. That is, there are exactly 256 different characters possible. This also implies that PHP has no native support of Unicode. See <a href="function.utf8-encode.html" class="function">utf8_encode()</a> and <a href="function.utf8-decode.html" class="function">utf8_decode()</a> for some basic Unicode functionality. </p> <blockquote><p><b class="note">Note</b>: <span class="simpara"> It is no problem for a <a href="language.types.string.html" class="type string">string</a> to become very large. PHP imposes no boundary on the size of a <a href="language.types.string.html" class="type string">string</a>; the only limit is the available memory of the computer on which PHP is running. </span> </p></blockquote> <div id="language.types.string.syntax" class="sect2"> <h3 class="title">Syntax</h3> <p class="para"> A <a href="language.types.string.html" class="type string">string</a> literal can be specified in four different ways: </p> <ul class="itemizedlist"> <li class="listitem"> <span class="simpara"> <a href="language.types.string.html#language.types.string.syntax.single" class="link">single quoted</a> </span> </li> <li class="listitem"> <span class="simpara"> <a href="language.types.string.html#language.types.string.syntax.double" class="link">double quoted</a> </span> </li> <li class="listitem"> <span class="simpara"> <a href="language.types.string.html#language.types.string.syntax.heredoc" class="link">heredoc syntax</a> </span> </li> <li class="listitem"> <span class="simpara"> <a href="language.types.string.html#language.types.string.syntax.nowdoc" class="link">nowdoc syntax</a> (since PHP 5.3.0) </span> </li> </ul> <div id="language.types.string.syntax.single" class="sect3"> <h4 class="title">Single quoted</h4> <p class="para"> The simplest way to specify a <a href="language.types.string.html" class="type string">string</a> is to enclose it in single quotes (the character <i>'</i>). </p> <p class="para"> To specify a literal single quote, escape it with a backslash (<i>\</i>). To specify a literal backslash before a single quote, or at the end of the <a href="language.types.string.html" class="type string">string</a>, double it (<i>\\</i>). Note that attempting to escape any other character will print the backslash too. </p> <blockquote><p><b class="note">Note</b>: <span class="simpara"> Unlike the two other syntaxes, <a href="language.variables.html" class="link">variables</a> and escape sequences for special characters will <em class="emphasis">not</em> be expanded when they occur in single quoted <a href="language.types.string.html" class="type string">string</a>s. </span> </p></blockquote> <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">echo </span><span style="color: #DD0000">'this is a simple string'</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #DD0000">'You can also have embedded newlines in <br />strings this way as it is<br />okay to do'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Outputs: Arnold once said: "I'll be back"<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'Arnold once said: "I\'ll be back"'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Outputs: You deleted C:\*.*?<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'You deleted C:\\*.*?'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Outputs: You deleted C:\*.*?<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'You deleted C:\*.*?'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Outputs: This will not expand: \n a newline<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'This will not expand: \n a newline'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Outputs: Variables do not $expand $either<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'Variables do not $expand $either'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </div> <div id="language.types.string.syntax.double" class="sect3"> <h4 class="title">Double quoted</h4> <p class="para"> If the <a href="language.types.string.html" class="type string">string</a> is enclosed in double-quotes ("), PHP will interpret more escape sequences for special characters: </p> <table border="5"> <caption><b>Escaped characters</b></caption> <colgroup> <thead valign="middle"> <tr valign="middle"> <th colspan="1">Sequence</th> <th colspan="1">Meaning</th> </tr> </thead> <tbody valign="middle" class="tbody"> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\n</i></td> <td colspan="1" rowspan="1" align="left">linefeed (LF or 0x0A (10) in ASCII)</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\r</i></td> <td colspan="1" rowspan="1" align="left">carriage return (CR or 0x0D (13) in ASCII)</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\t</i></td> <td colspan="1" rowspan="1" align="left">horizontal tab (HT or 0x09 (9) in ASCII)</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\v</i></td> <td colspan="1" rowspan="1" align="left">vertical tab (VT or 0x0B (11) in ASCII) (since PHP 5.2.5)</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\f</i></td> <td colspan="1" rowspan="1" align="left">form feed (FF or 0x0C (12) in ASCII) (since PHP 5.2.5)</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\\</i></td> <td colspan="1" rowspan="1" align="left">backslash</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\$</i></td> <td colspan="1" rowspan="1" align="left">dollar sign</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\"</i></td> <td colspan="1" rowspan="1" align="left">double-quote</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\[0-7]{1,3}</i></td> <td colspan="1" rowspan="1" align="left"> the sequence of characters matching the regular expression is a character in octal notation </td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left"><i>\x[0-9A-Fa-f]{1,2}</i></td> <td colspan="1" rowspan="1" align="left"> the sequence of characters matching the regular expression is a character in hexadecimal notation⌨️ 快捷键说明
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