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<?php function is_valid($string) { return preg_match('~(\((?1)*+\)|\[(?1)*+]|{(?1)*+})*\z~A', $string); } $expressions = array(")(){}", "[]({})", "([])", "{()[]}", "([)]", "{()[]}{()[]}{()[]}{()[]}{()[]}"); foreach ($expressions as $expression) { echo "$expression is " , is_valid($expression) , "\n"; }
Output for git.master_jit, git.master, rfc.property-hooks
)(){} is 0 []({}) is 1 ([]) is 1 {()[]} is 1 ([)] is 0 {()[]}{()[]}{()[]}{()[]}{()[]} is 1

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