Question

<?php echo $form->create(); ?> 
   <?php echo $form->hidden('id'); ?> 
   <?php echo $form->input('name')); ?> 
   <?php echo $form->submit('Save'); ?> 
<?php echo $form->end(); ?>   

I want to replace “; ?” with ” ?”.

I used the vi command “:%s/; \?/ \?/g” to do that. I got the following output

<?php echo $form->create() ??> 
   <?php echo $form->hidden('id') ??> 
   <?php echo $form->input('name')) ??> 
   <?php echo $form->submit('Save') ??> 
<?php echo $form->end() ??> 

Actually, I need the following output.

<?php echo $form->create() ?>
   <?php echo $form->hidden('id') ?>
   <?php echo $form->input('name')) ?>
   <?php echo $form->submit('Save') ?>
<?php echo $form->end() ?>

Can you give the explanation for this strange behavior?

Answer 1

The \? is the vi-regular-expression for the normal ? in other program’s regular expressions.

You can look at :h regex to verify this (or more precisely :h E61).

So when using ; \? you match ; (no space) and ;<space> (one space). From these matches the greediest one (see E61 – as many as possible) will be replaced with a ? thus resulting in two question-marks (one new one and the old one) when there is a space present.

The correct expression would be: s/; ?/ ?/g

EDIT: Fixed explanation to be more precise.