title: PHP insert keys in string
body: <p>I have the following string:</p>
  
  <pre><code>{"1":"http://localhost:8888/classecar/uploads/dropzone/ferrari1.jpg","2":"http://localhost:8888/classecar/uploads/dropzone/ferrari2.jpg","3":"http://localhost:8888/classecar/uploads/dropzone/ferrari3.jpg","4":"http://localhost:8888/classecar/uploads/dropzone/ferrari4.jpg"}
  </code></pre>
  
  <p>How can I  get rid of the numbers preceding "http..." and transform this same numbers in array <em>keys</em>?</p>
  
  <p>Like this:</p>
  
  <pre><code>[0] =&gt; "http...", 
  [1] =&gt; "http...", 
  [2] =&gt; "http...",
  </code></pre>