Why str_replace returns wrong data

Example: Replace English commas, space characters, or Chinese commas
$str = 'Correct, contact us goodsjob, goodsjob';
$reg = array(',',' ',',' );
$strs = ' username like %'.str_replace($reg,'%, or username like %',$str).'%';
The returned data is: username like %correct%,%, or username like %or%, or username like %username%, or username like %like%, or username like % Contact Us%, or username like %goodsjob%, or username like %goodsjob%, why?

The correct result should be: usernme like %correct%, or username like %contact us%, or username like %goodsjob%

Reply content:

Example: Replace English commas, space characters, or Chinese commas
$str = 'Correct, contact us goodsjob, goodsjob';
$reg = array(',',' ',',' );
$strs = ' username like %'.str_replace($reg,'%, or username like %',$str).'%';
The returned data is: username like %correct%,%, or username like %or%, or username like %username%, or username like %like%, or username like % Contact Us%, or username like %goodsjob%, or username like %goodsjob%, why?

The correct result should be: usernme like %correct%, or username like %contact us%, or username like %goodsjob%

First replace the spaces with other characters. During the replacement process, $str =》%, or username like %. There are also strings that meet your replacement rules, so it will affect the result

        $str = '正确,联系我们 goodsjob，goodsjob';
        $str = str_replace(' ', ' ', $str);
        $reg = array(',','，'," ");
        $strs = 'username like %'.str_replace($reg,'%, or username like %',$str).'%';
        
        

Note: Since the str_replace() function replaces left to right, it may replace previously inserted values ​​when doing multiple replacements.