Online PHP editor | output for BJDgY

<?php function do_split($name) { return preg_split('/([A-Z]{2,}|([A-Z][^A-Z]*))/', $name, null, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY); } function convert_case($name) { return implode( '_', array_map( 'strtolower', do_split($name) ) ); } function convert_case2($name) { $length = strlen($name); if ($length < 2) { return strtolower($name); } $output = ''; // init stream $prev_val = '_'; $prev_upr = false; $char_val = $name[0]; $char_upr = ctype_upper($char_val); for ($i = 0; $i < $length; $i++) { // peek $next_val = $i+1 < $length ? $name[$i+1] : '_'; $next_upr = ctype_upper($next_val); if ($prev_val == '_') { if ($char_val == '_') { continue; } $output .= $char_val; } else if ($char_upr !== $prev_upr) { $output .= '_'.$char_val; } else if ($char_upr && !$next_upr && $next_val !== '_') { // && $prev_upr $output .= $char_val.'_'; $char_val = '_'; $char_upr = false; } else { $output .= $char_val; } // roll over $prev_val = $char_val; $prev_upr = $char_upr; $char_val = $next_val; $char_upr = $next_upr; } return strtolower($output); } convert_case2('FooBARbar0123'); $samples = array( 'FooBar', 'FooBAR', 'FOOBar', 'foo_bar', 'FOO_bar', 'FOO_Bar', 'foo_BAR', 'foo_Bar', 'Foo_bar', ); /* print_r(array_map(function ($name) { return array( 'name' => $name, 'split' => do_split($name), 'converted' => convert_case($name), ); }, $samples)); */