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run code in 150+ php & hhvm versions
Bugs & Features
<?php function isCorrect($string) { $len = strlen($string); $stack = array(); for( $i = 0; $i < $len; ++$i) { if ( $string[$i] == '(' ) array_push($stack, $string[$i]); elseif( $string[$i] == ')' ) { if ( empty($stack) === false ) array_pop($stack); else return false; } } return empty($stack); } $string = '()((()))'; var_dump(isCorrect($string)); //var_dump(isCorrect($string)); //var_dump(strlen($string) % 2); //assert(isCorrect('') === true); //assert(isCorrect('()') === true); //assert(isCorrect('{()}') === true); //assert(isCorrect('{()}{}') === true); //assert(isCorrect('(())') === true); //assert(isCorrect('{({({({()})})})}') === true); //assert(isCorrect('{(})') === false);
based on tYCvK
Output for 4.3.0 - 5.0.5, 5.1.1 - 5.6.28, hhvm-3.12.0, 7.0.0 - 7.1.0
bool(true)
Output for hhvm-3.10.0

Process exited with code 153.
Output for 5.1.0
Fatal error: fatal flex scanner internal error--end of buffer missed in /in/83isr on line 28
Process exited with code 255.