title: PHP Regex pattern to get a specify word
body: <p>i have some strings result of <code>var_dump</code> like this :</p>
  
  <pre><code>string(5) "tes37"
  string(6) "SRV410"
  string(6) "SRV400"
  string(6) "SRV311"
  string(6) "SRV302"
  string(6) "SRV301"
  string(6) "SRV300"
  string(6) "SRV001"
  string(7) "SRV_123"
  string(5) "sad34"
  string(7) "S 0001J"
  string(8) "S 00004J"
  string(8) "S 00003J"
  string(8) "S 00002J"
  string(6) "asdasd"
  string(4) "4356"
  string(3) "234"
  </code></pre>
  
  <p>here i want to get string with regex such as : 
  S 0001J, S 00002J, S 00003J and S00004J</p>
  
  <p>anyone can help me out to make the pattern regex ? 
  Thank you </p>