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<?php $x = '.'; $a = ''; for ($i=0;$i<1000000;$i++) $a = "$a$x"; unset($a,$x); echo memory_get_usage()."\n";
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.7

Process exited with code 137.
preferences:
149.8 ms | 404 KiB | 215 Q