title: php preg_replace string doesn't work
body: <p>I have tried to minify a json file with str_replace() but that doesn't work well as I used it. </p>
  
  <pre><code>//I want to minify a json file with php. 
  //Here I am trying to replace ", {" with ",{"
  
  //$result = preg_replace('/abc/', 'def', $string);   # Replace all 'abc' with 'def'
  
  $new = preg_replace('/, {/', ',{', $new); //doesn't work.. why?
  </code></pre>