How does PHP memory actually work

Question

I\'ve always heard and searched for new php \'good writing practice\', for example: It\'s better (for performance) to check if array key exists than search in array, but als

Answer 1

From PHP manual Garbage Collection http://php.net/manual/en/features.gc.php

gc_enable(); // Enable Garbage Collector
var_dump(gc_enabled()); // true
var_dump(gc_collect_cycles()); // # of elements cleaned up
gc_disable(); // Disable Garbage Collector

PHP does not return released memory very well; Its primary usage online does not require it and effective garbage collection takes time away from providing the output; When the script ends the memory is going to be returned anyway.

Garbage collection happens.

1. When you tell it to

   int gc_collect_cycles ( void )

2. When you leave a function

3. When the script ends

Better understanding of PHP's Garbage collection from a web host, (no affiliation). http://www.sitepoint.com/better-understanding-phps-garbage-collection/

If you are considering byte by byte how the data is set in memory. Different ports are going to effect those values. 64bit CPUs performance is best when data sits on the first bit of a 64bit word. For the max performance a specific binary they would allocate the start of a block of memory on the first bit, leaving up to 7 bytes unused. This CPU specific stuff depends on what compiler was used to compile the PHP.exe. I can not offer any way to predict exact memory usage, given that it will be determined differently by different compilers.

Alma Do, post goes to the specifics of the source which is sent to the compiler. What the PHP source requests and the compiler optimizes.

Looking at the specific examples you posted. When the key is a ascii letter they are taking 4 bytes (64 bits) more per entry ... this suggests to me, (assuming no garbage or memory holes, ect), that the ascii keys are greater than 64 bits, but the numeric keys are fit in a 64bit word. It suggests to me your using a 64bit computer and your PHP.exe is compiled for 64bit CPUs.