PHP unset () detailed

Introduction: This is a detailed page of PHP unset () details, introduced and Php,unset, PHP php unset () detailed knowledge, skills, experience, and some PHP source code and so on.

class= ' pingjiaf ' frameborder= ' 0 ' src= ' http://biancheng.dnbcw.info/pingjia.php?id=361000 ' scrolling= ' no ' > 1. If more than one variable name points to a variable value, unset any one variable name simply disconnects the relationship between the variable name and the variable value, does not free memory, and the value exists
(see 2 for exceptions).
2. Two cases will release memory, otherwise the value of the variable in memory still exists.
A) When the value of the variable takes up more than 256 bytes, the memory is freed by unset () (This is someone's test result, to be explained)
b) When all variables that point to the value (such as a reference variable pointing to the value) are destroyed
3. If you want to release the variable memory, it is best to release it with $a=null, when the null value is assigned, the address is freed, all references to the variable value are empty
4. When a global variable is unset in the local environment, the global variable is only invalidated at the local scope. Unchanged in other places

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