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    <p>One primary need I have for late static binding is for a set of static instance-creation methods. </p> <p>This <a href="http://harmoni.sourceforge.net/harmoniDoc/phpdoc/harmoni/primitives.chronology/DateAndTime.html" rel="nofollow noreferrer">DateAndTime class</a> is part of a chronology library that I ported to PHP from Smalltalk/Squeak. Using static instance-creation methods enables creation of instances with a variety of argument types, while keeping parameter checking in the static method so that the consumer of the library is unable to obtain an instance that is not fully valid. </p> <p>Late static binding is useful in this case so that the implementations of these static instance-creation methods can determine what class was originally targeted by the call. Here is an example of usage:</p> <p><strong>With LSB:</strong></p> <pre><code>class DateAndTime { public static function now() { $class = static::myClass(); $obj = new $class; $obj-&gt;setSeconds(time()); return $obj; } public static function yesterday() { $class = static::myClass(); $obj = new $class; $obj-&gt;setSeconds(time() - 86400); return $obj; } protected static function myClass () { return 'DateAndTime'; } } class Timestamp extends DateAndTime { protected static function myClass () { return 'Timestamp'; } } // Usage: $date = DateAndTime::now(); $timestamp = Timestamp::now(); $date2 = DateAndTime::yesterday(); $timestamp2 = Timestamp::yesterday(); </code></pre> <p>Without late static binding, [as in my current implementation] each class must implement every instance creation method as in this example:</p> <p><strong>Without LSB:</strong></p> <pre><code>class DateAndTime { public static function now($class = 'DateAndTime') { $obj = new $class; $obj-&gt;setSeconds(time()); return $obj; } public static function yesterday($class = 'DateAndTime') { $obj = new $class; $obj-&gt;setSeconds(time() - 86400); return $obj; } } class Timestamp extends DateAndTime { public static function now($class = 'Timestamp') { return self::now($class); } public static function yesterday($class = 'Timestamp') { return self::yesterday($class); } } </code></pre> <p>As the number of instance-creation methods and class-hierarchy increases the duplication of methods becomes a real pain in the butt. LSB reduces this duplication and allows for much cleaner and more straight-forward implementations.</p>
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    1. USAdam Franco
    1. USAdam Franco
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