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run code in 300+ PHP versions simultaneously
<?php $a = [1, 2]; $b = $a; $a[] = 3; $b[] = 4; echo "When next index=2 and max key=2, next key is both 2.\n"; var_dump($a, $b); // $a = [0=>1, 1=>2, 2=>3] $b = [0=>1, 1=>2, 2=>4] $a = [1, 2]; unset($a[1]); $b = $a; $a[] = 3; $b[] = 4; echo "\nWhen next index=2 and max key=1, next key is both 2. \n"; var_dump($a, $b); // $a = [0=>1, 2=>3] $b = [0=>1, 2=>4] $a = [1, 2]; unset($a[1], $a[0]); $b = $a; $a[] = 3; $b[] = 4; echo "\nWhen next index=2 and max key=0, next key is 0 or 2."; var_dump($a, $b); // $a = [0=>3] $b = [2=>4] what? $a = [1, 2]; unset($a[1], $a[0]); $b = $a; $b[] = 4; $a[] = 3; echo "\nIf reverse variable, result is reverse too.\n"; var_dump($a, $b); // $a = [2=>3] $b = [0=>4] what?? $a = [1, 2]; unset($a[1], $a[0]); $b = $c = $d = $a; $a[] = 3; $b[] = 4; $d[] = 6; $c[] = 5; echo "\nWhen increase variables, only the last one take over key..\n"; var_dump($a, $b, $c, $d); // $c's key is 2, others are 0
Output for 5.4.34 - 5.4.45, 5.5.18 - 5.5.38, 5.6.1 - 5.6.40, 7.3.17 - 7.3.33, 7.4.5 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.4, 8.3.6
When next index=2 and max key=2, next key is both 2. array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(3) } array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(4) } When next index=2 and max key=1, next key is both 2. array(2) { [0]=> int(1) [2]=> int(3) } array(2) { [0]=> int(1) [2]=> int(4) } When next index=2 and max key=0, next key is 0 or 2.array(1) { [2]=> int(3) } array(1) { [2]=> int(4) } If reverse variable, result is reverse too. array(1) { [2]=> int(3) } array(1) { [2]=> int(4) } When increase variables, only the last one take over key.. array(1) { [2]=> int(3) } array(1) { [2]=> int(4) } array(1) { [2]=> int(5) } array(1) { [2]=> int(6) }
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0 When next index=2 and max key=2, next key is both 2. array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(3) } array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(4) } When next index=2 and max key=1, next key is both 2. array(2) { [0]=> int(1) [2]=> int(3) } array(2) { [0]=> int(1) [2]=> int(4) } When next index=2 and max key=0, next key is 0 or 2.array(1) { [2]=> int(3) } array(1) { [2]=> int(4) } If reverse variable, result is reverse too. array(1) { [2]=> int(3) } array(1) { [2]=> int(4) } When increase variables, only the last one take over key.. array(1) { [2]=> int(3) } array(1) { [2]=> int(4) } array(1) { [2]=> int(5) } array(1) { [2]=> int(6) }
Output for 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.16, 7.4.0 - 7.4.4
When next index=2 and max key=2, next key is both 2. array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(3) } array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(4) } When next index=2 and max key=1, next key is both 2. array(2) { [0]=> int(1) [2]=> int(3) } array(2) { [0]=> int(1) [2]=> int(4) } When next index=2 and max key=0, next key is 0 or 2.array(1) { [0]=> int(3) } array(1) { [2]=> int(4) } If reverse variable, result is reverse too. array(1) { [2]=> int(3) } array(1) { [0]=> int(4) } When increase variables, only the last one take over key.. array(1) { [0]=> int(3) } array(1) { [0]=> int(4) } array(1) { [2]=> int(5) } array(1) { [0]=> int(6) }
Output for 5.4.0 - 5.4.33, 5.5.0 - 5.5.17, 5.6.0
When next index=2 and max key=2, next key is both 2. array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(3) } array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(4) } When next index=2 and max key=1, next key is both 2. array(2) { [0]=> int(1) [1]=> int(3) } array(2) { [0]=> int(1) [2]=> int(4) } When next index=2 and max key=0, next key is 0 or 2.array(1) { [0]=> int(3) } array(1) { [2]=> int(4) } If reverse variable, result is reverse too. array(1) { [2]=> int(3) } array(1) { [0]=> int(4) } When increase variables, only the last one take over key.. array(1) { [0]=> int(3) } array(1) { [0]=> int(4) } array(1) { [2]=> int(5) } array(1) { [0]=> int(6) }
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29
Parse error: syntax error, unexpected '[' in /in/TYc10 on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5
Parse error: parse error, unexpected '[' in /in/TYc10 on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/TYc10 on line 3
Process exited with code 255.

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