title: using php preg_replace to replace a whole character string and not replace if string is part of a longer string
body: <p>Regular Expressions are completely new to me and having done much searching my expression for testing purposes is this:</p>
  
  <pre><code>preg_replace('/\b0.00%\b/','- ', '0.00%')
  </code></pre>
  
  <p>It yields <code>0.00%</code> when what I want is <code>- </code>.</p>
  
  <p>With <code>preg_replace('/\b0.00%\b/','- ', '50.00%')</code> yields <code>50.00%</code> which is what I want - so this is fine.</p>
  
  <p>But clearly the expression is not working as it is not, in the first example replacing <code>0.00%</code> with <code>-</code>.</p>
  
  <p>I can think of workarounds with <code>if(){}</code> for testing length/content of string but presume the replace will be most efficient</p>