3v4l.org

run code in 300+ PHP versions simultaneously
<?php $records = array( array( 'id' => 2135, 'first_name' => 'John', 'last_name' => 'Doe', ), array( 'id' => 3245, 'first_name' => 'Sally', 'last_name' => 'Smith', ), array( 'id' => 5342, 'first_name' => 'Jane', 'last_name' => 'Jones', ), array( 'id' => 5623, 'first_name' => 'Peter', 'last_name' => 'Doe', ) ); $keys = array_keys($records[0]); var_export($keys); echo "\n"; echo "Number of columns: " , count($keys);

preferences:
28.05 ms | 405 KiB | 5 Q