替换字符串PHP REGEX中的模式

Question

I have a string that is used for an INSERT command. When values are empty, the corresponding spot in the INSERT string is being generated as:

VALUES ('', 'VALUE', '', '', '', 0, 1, '')

I want to replace the '' with NULL so the database no longer throws an error about casting varchar to type numeric :

VALUES (null, 'VALUE', null, null, null, 0, 1, null)

I tried using:

$build_values_m = str_replace($build_values_m, ", '', ", ", null, ");

However, that takes away most of my INSERT string and does not JUST replace the empty values with NULL .

How can I do this?

Answer 1

It looks like you want to replace "''" with "NULL" and that you are attempting to do so without glancing at the manual: http://php.net/manual/en/function.str-replace.php

If you looked at the manual, you would see that the order of the parameters is Search, Replace, OriginalString. You are trying to do OriginalString, Search, Replace - which won't work - obviously. So, try to do it in the proper order:

$build_values_m = str_replace("''","NULL",$build_values_m);

Then, all instances of "''" will be replaced with the string "NULL" .

Answer 2

You can perform replacement using regex replacement function preg_replace() like following :

$string = "VALUES ('','','VALUE HERE','',)";
$pattern = array();
$pattern[0] = '/\'\'/g'; // Match : ''
$replacement = array();
$replacement[0] = 'NULL';

preg_replace($pattern, $replacement, $string);