PHP magic method learning. _ Set_state () var_export can export a set as a string that is executable PHP code. In the object-oriented PHP 5.1.0, a parameter named _ set_stat _ set_state () is introduced ()
Var_export can export a set as a string, which is some executable PHP code. In php5.1.0, a static method named _ set_state is introduced to make var_export support exporting object instances. When you use var_export to export an instance, the exported string contains the code that calls this static method. This method has a parameter, which is an array containing all member attributes of the exported instance. A little abstract. let's look at the example below.
$ V) {$ obj-> $ k = $ v;} return $ obj ;}}$ I = new o; $ I-> age = 21; eval ('$ B = '. var_export ($ I, true ). ';'); // true indicates that var_export returns the exported string instead of printing it out. Print_r ($ B);/* output: stdClass Object ([skill] => php [age] => 21) */?>
_ Clone ()
In php5, the value assignment between objects is always transmitted by address reference. For example, the following example will output 66 instead of 55.
Age = 66; echo $ i2-> age;?>
If you want to pass the information using the actual value, you need to use the clone keyword.
Age = 66; echo $ i2-> age; // output 55?>
However, the instance $ I is cloned here. If a member attribute of $ I is also an instance, this member attribute will still be passed to $ i2 as a reference method. For example:
Sub = new o2; $ i2 = clone $ I; $ I-> sub-> p = 5; echo $ i2-> sub-> p;?>
The final output is 5 rather than 1. That is to say, although $ I and $ i2 do not point to the same instance, their member attribute $ sub points to the same instance. At this time, we must use the _ clone method to copy $ sub. Add the _ clone () method to the o class. As follows:
Sub = clone $ this-> sub; }}// ......?>
In this way, when echo $ i2-> sub-> p;, the value 1 is output.
_ Autoload ()
When you create an instance, if the corresponding class does not exist, __autoload () will be executed. this function has a parameter for the class name corresponding to the instance to be created. In the following example, if/home/surfchen/project/auto. if php exists, the file require. Otherwise, an error of Class test Not Found is printed and the current script is aborted.
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