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<?php function decrement($str) { $index = strlen($str)-1; $ord = ord($str[$index]); if ($ord > 65) { // The final character is still greater than A, decrement return substr($str, 0, $index) . chr($ord-1); } if ($index > 0) { // Strip the final 2 characters and append a Z return substr($str, 0, $index-1) . 'Z'; } // Can't be decremented return false; } var_dump( decrement('A'), decrement('AA'), decrement('AAAA'), decrement('XXXZ') );
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
bool(false) string(1) "Z" string(3) "AAZ" string(4) "XXXY"
preferences:
94.42 ms | 1994 KiB | 4 Q