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<?php $s = ''; $s[4] = 1; var_dump($s);
Output for 7.1.0 - 7.1.25, 7.2.0 - 7.2.31, 7.3.0 - 7.3.19, 7.4.0 - 7.4.8, 8.0.0alpha1 - alpha2
string(5) " 1"
Output for 7.0.0 - 7.0.20
array(1) { [4]=> int(1) }