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| | | <glacius:metadata> |
| | | <title>string.Format() in PHP</title> |
| | | <description>Implementation of .NET-style string.Format() in PHP</description> |
| | | <category>PHP</category> |
| | | <category>C#</category> |
| | | <category>Programming</category> |
| | | <category>Legacy blog posts</category> |
| | | </glacius:metadata> |
| | | |
| | | <glacius:macro name="legacy blargh banner"> |
| | | <properties> |
| | | <originalUrl>https://tmont.com/blargh/2010/1/string-format-in-php</originalUrl> |
| | | <originalDate>2010-01-09T22:22:08.000Z</originalDate> |
| | | </properties> |
| | | </glacius:macro> |
| | | |
| | | <p> |
| | | .NET's <a href="https://www.php.net/sprintf"><code>sprintf()</code></a> |
| | | <a href="https://docs.microsoft.com/en-us/dotnet/api/system.string.format?view=net-6.0">equivalent</a> |
| | | has ordered parameters. |
| | | </p> |
| | | |
| | | <glacius:code lang="csharp"><![CDATA[var s = string.Format("My name is {1}, {0}", "Tommy", "Montgomery"); |
| | | //s = "My name is Montgomery, Tommy" |
| | | <glacius:code lang="csharp"><![CDATA[var s = string.Format("My name is {1}, {0}", "John", "Doe"); |
| | | //s = "My name is Doe, John" |
| | | |
| | | var s = string.Format("My name is {{{0}}}", "Tommy"); |
| | | //s = "My name is {Tommy}"]]></glacius:code> |
| | | var s = string.Format("My name is {{{0}}}", "John"); |
| | | //s = "My name is {John}"]]></glacius:code> |
| | | |
| | | <p>I needed that. Here it is, PHPified:</p> |
| | | |
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| | | <glacius:code lang="php"><![CDATA[function format($format) { |
| | | $args = func_get_args(); |
| | | $format = array_shift($args); |
| | | |
| | | preg_match_all('/(?=\{)\{(\d+)\}(?!\})/', $format, $matches, PREG_OFFSET_CAPTURE); |
| | | $offset = 0; |
| | | foreach ($matches[1] as $data) { |
| | | $i = $data[0]; |
| | | $format = substr_replace($format, @$args[$i], $offset + $data[1] - 1, 2 + strlen($i)); |
| | | $offset += strlen(@$args[$i]) - 2 - strlen($i); |
| | | } |
| | | |
| | | return $format; |
| | | }]]></glacius:code> |
| | | |
| | | <p> |
| | | There's a lot going on in here that isn't used very often in PHP. Here is a terse |
| | | explanation of the not-so-obvious features: |
| | | </p> |
| | | |
| | | <ul> |
| | | <li> |
| | | The <a href="http://php.net/manual/en/pcre.constants.php"><code>PREG_OFFSET_CAPTURE</code></a> |
| | | The <a href="https://www.php.net/manual/en/pcre.constants.php#constant.preg-offset-capture"><code>PREG_OFFSET_CAPTURE</code></a> |
| | | constant tells the regex engine to capture the string index offset of each match. |
| | | </li> |
| | | <li> |
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| | | <code>(?=\{)</code> and <code>(?!\})</code> in the regular expression are |
| | | <a href="https://www.regular-expressions.info/lookaround.html">positive and negative lookarounds</a>, |
| | | respectively. The nice thing about that is they're also zero-width matching, which means they |
| | | won't be returned as part of the match result. These are needed because to output a |
| | | literal <code>{</code> in a C# string you precede it with another <code>{</code> (a little known |
| | | fact about C#). |
| | | </li> |
| | | <li> |
| | | <a href="https://www.php.net/manual/en/function.substr-replace.php"><code>substr_replace</code></a> is |
| | | an infrequently used, extremely useful function, that replaces a substring within a string, |
| | | expanding to the given width. |
| | | </li> |
| | | <li> |
| | | The <code>$offset</code> variable tracks the string length delta. Since we're modifying the |
| | | string, the offsets captured in the regex match becomes out of date. |
| | | </li> |
| | | </ul> |
| | | </ul> |