3v4l.org

run code in 300+ PHP versions simultaneously
<?php $headers = <<<HEADERS # Hello ## World ### Let's add ## Some headers ### Yay! # Foo ## Bar ## Bar Again HEADERS; $levels = []; echo preg_replace_callback( '~^(#+)\K~m', function($m) use (&$levels) { $hashes = strlen($m[1]); $index = $hashes - 1; $reduction = sizeof($levels) - $hashes; if (!isset($levels[$index])) { $levels[$index] = 1; } else { ++$levels[$index]; } if ($reduction > 0) { $levels = array_slice($levels, 0, -$reduction); } return " " . implode('.', $levels); }, $headers );
Output for 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
# 1 Hello ## 1.1 World ### 1.1.1 Let's add ## 1.2 Some headers ### 1.2.1 Yay! # 2 Foo ## 2.1 Bar ## 2.2 Bar Again
preferences:
144.47 ms | 407 KiB | 5 Q