PHP 5.2, late static binding, get_called_class() and $self = new self()
Early on in Septuro’s development, well prior to the name being adopted, I had a tough challenge dealing with the dataTemplates. Chris Webb, one of the Septuro founders, was helping me with this particular issue. In the abstract dataTemplate, we wanted to set up a factory method make() that just pumped out an instance of the class that was called. The issue that we ran into involved late static binding.
class abstract_dataTemplate {
static function make() {
return new self();
}
}
class stringTemplate extends abstract_dataTemplate {
}
stringTemplate::make();
In this example, we called stringTemplate::make(), but since make() is defined within abstract_dataTemplate, the function will always return an instance of abstract_dataTemplate. We found out that in PHP 5.3, late static binding will be better supported and come with a function get_called_class() that will return the name of the called class, rather than the current class. Unfortunately, we run PHP 5.2 on our servers and are unable to use this function. I considered using debug_backtrace(), file() and preg_match() to mimic the functionality, but this won’t work if there is more than 1 instance per line of a late static bind call.
I looked at php.net to see if anyone else found a good solution, but everyone seemed to be stopped at the same point I was. Then I realized I could use static class properties to keep a count of how many times a match has already been found on the current line. This would let me support multiple calls per line without issue – with each call returning the exact class that called it. So I took a function listed in the php.net comments and modified it up to make use of this static class.
if(!function_exists('get_called_class')) {
class class_tools {
static $i = 0;
static $fl = null;
static function get_called_class() {
$bt = debug_backtrace();
if(self::$fl == $bt[2]['file'].$bt[2]['line']) {
self::$i++;
} else {
self::$i = 0;
self::$fl = $bt[2]['file'].$bt[2]['line'];
}
$lines = file($bt[2]['file']);
preg_match_all('
/([a-zA-Z0-9\_]+)::'.$bt[2]['function'].'/',
$lines[$bt[2]['line']-1],
$matches
);
return $matches[1][self::$i];
}
}
function get_called_class() {
return class_tools::get_called_class();
}
}
We now have perfect support of get_called_class() in PHP 5.2, and we can use the factory method make() inside the abstract dataTemplate, rather than in all of the derived templates.
