SH, LD, RD, PATH_CACHE, etc.</em></p>
<p><strong>INCORRECT</strong>:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nx">myConstant</span>      <span class="c1">// missing underscore separator and not fully uppercase</span>
<span class="nx">N</span>               <span class="c1">// no single-letter constants</span>
<span class="nx">S_C_VER</span>         <span class="c1">// not descriptive</span>
<span class="nv">$str</span> <span class="o">=</span> <span class="nb">str_