title: PHP json_encode produces quoted json but JS expects it to be without quotes
body: <p>What I need:</p>
  
  <pre><code>[
       {label:'Hotel'},
       {label:'Event Regristration'},
       {label:'Airfare'}
  ]
  </code></pre>
  
  <p>what is generated by my code</p>
  
  <pre><code>[
       {'label':'Hotel'},
       {'label':'Event Regristration'},
       {'label':'Airfare'}
  ]
  </code></pre>
  
  <p>with</p>
  
  <pre><code>$series[]['label'] = "some value";
  </code></pre>
  
  <p>Is there a difference between the to json examples? Actually the first one is working with jqPlot and the second one not. Any ideas how can remove the quotes? Other suggestions?</p>