[php-src] Issue #8896: Magic with memory usage or array

Issue: https://github.com/php/php-src/issues/8896 Author: woodholly ### Description The following code: ```php <?php $a = array(); for($i=1; $i<=1000000;$i++) { $a[$i] = var_export(array("foobar$i"), true); } echo "done, memory usage = " . (memory_get_usage(true)/1024/1024) . "Mb\n"; ``` Resulted in this output: ``` done, memory usage = 278.00390625Mb ``` But this code with var_export casted to "real" string: ```php <?php $a = array(); for($i=1; $i<=1000000;$i++) { $a[$i] = "" . var_export(array("foob(ar$i"), true); } echo "done, memory usage = " . (memory_get_usage(true)/1024/1024) . "Mb\n"; ``` Resulted in this output: ``` done, memory usage = 94.00390625Mb ``` 1) Why original var_export eats x3 more memory in comparison with string-casted variant ? (same thing with json_encode) 2) Why casting using (string) does not help ? What kind of magic is working here ? ### PHP Version PHP 7.4 ### Operating System Ubuntu