title: how to decrement a part in a value of an array?
body: <p>i have an array in the format</p>
  
  <pre><code>array() {["2011-07-29"]=&gt; 39 ["2011-07-30"]=&gt; 39 ["2011-07-31"]=&gt; 39 ["2011-08-01"]=&gt; 40}
  </code></pre>
  
  <p>i need t0 decrement the middle keyvalue by 1 i.e ["2011-<strong><em>07</em></strong>-29"] to ["2011-<strong><em>06</em></strong>-29"]</p>
  
  <p>the output should be</p>
  
  <pre><code>array() {["2011-06-29"]=&gt; 39 ["2011-06-30"]=&gt; 39 ["2011-06-31"]=&gt; 39 ["2011-07-01"]=&gt; 40}
  </code></pre>
  
  <p>how to do this?</p>