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<?php var_dump( ${!${'0'} = 'StdClass'} );
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
Warning: Undefined variable $ in /in/NMpEQ on line 4 NULL
Output for 5.5.24 - 5.5.35, 5.6.8 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.16 - 7.3.31, 7.4.0 - 7.4.33
Notice: Undefined variable: in /in/NMpEQ on line 4 NULL
Output for 7.3.32 - 7.3.33
NULL

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137.9 ms | 401 KiB | 177 Q